diff --git a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
index ac4bd6da0b..43d5d081a8 100644
--- a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
+++ b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/FrameworkExtension.php
@@ -1011,7 +1011,10 @@ class FrameworkExtension extends Extension
             $container->register('routing.loader.annotation', AnnotatedRouteControllerLoader::class)
                 ->setPublic(false)
                 ->addTag('routing.loader', ['priority' => -10])
-                ->addArgument(new Reference('annotation_reader', ContainerInterface::NULL_ON_INVALID_REFERENCE));
+                ->setArguments([
+                    new Reference('annotation_reader', ContainerInterface::NULL_ON_INVALID_REFERENCE),
+                    '%kernel.environment%',
+                ]);
 
             $container->register('routing.loader.annotation.directory', AnnotationDirectoryLoader::class)
                 ->setPublic(false)
diff --git a/src/Symfony/Bundle/FrameworkBundle/Kernel/MicroKernelTrait.php b/src/Symfony/Bundle/FrameworkBundle/Kernel/MicroKernelTrait.php
index 52587cc7c7..c77c452d99 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Kernel/MicroKernelTrait.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Kernel/MicroKernelTrait.php
@@ -152,7 +152,7 @@ trait MicroKernelTrait
             };
 
             try {
-                $this->configureContainer(new ContainerConfigurator($container, $kernelLoader, $instanceof, $file, $file), $loader);
+                $this->configureContainer(new ContainerConfigurator($container, $kernelLoader, $instanceof, $file, $file, $this->getEnvironment()), $loader);
             } finally {
                 $instanceof = [];
                 $kernelLoader->registerAliasesForSinglyImplementedInterfaces();
@@ -193,7 +193,7 @@ trait MicroKernelTrait
             return $routes->build();
         }
 
-        $this->configureRoutes(new RoutingConfigurator($collection, $kernelLoader, $file, $file));
+        $this->configureRoutes(new RoutingConfigurator($collection, $kernelLoader, $file, $file, $this->getEnvironment()));
 
         foreach ($collection as $route) {
             $controller = $route->getDefault('_controller');
diff --git a/src/Symfony/Bundle/FrameworkBundle/Resources/config/routing.php b/src/Symfony/Bundle/FrameworkBundle/Resources/config/routing.php
index bd44427bf6..09e340ff8a 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Resources/config/routing.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Resources/config/routing.php
@@ -49,36 +49,42 @@ return static function (ContainerConfigurator $container) {
         ->set('routing.loader.xml', XmlFileLoader::class)
             ->args([
                 service('file_locator'),
+                '%kernel.environment%',
             ])
             ->tag('routing.loader')
 
         ->set('routing.loader.yml', YamlFileLoader::class)
             ->args([
                 service('file_locator'),
+                '%kernel.environment%',
             ])
             ->tag('routing.loader')
 
         ->set('routing.loader.php', PhpFileLoader::class)
             ->args([
                 service('file_locator'),
+                '%kernel.environment%',
             ])
             ->tag('routing.loader')
 
         ->set('routing.loader.glob', GlobFileLoader::class)
             ->args([
                 service('file_locator'),
+                '%kernel.environment%',
             ])
             ->tag('routing.loader')
 
         ->set('routing.loader.directory', DirectoryLoader::class)
             ->args([
                 service('file_locator'),
+                '%kernel.environment%',
             ])
             ->tag('routing.loader')
 
         ->set('routing.loader.container', ContainerLoader::class)
             ->args([
                 tagged_locator('routing.route_loader'),
+                '%kernel.environment%',
             ])
             ->tag('routing.loader')
 
diff --git a/src/Symfony/Bundle/FrameworkBundle/composer.json b/src/Symfony/Bundle/FrameworkBundle/composer.json
index 0f66c585ed..5cada9c672 100644
--- a/src/Symfony/Bundle/FrameworkBundle/composer.json
+++ b/src/Symfony/Bundle/FrameworkBundle/composer.json
@@ -19,7 +19,7 @@
         "php": ">=7.2.5",
         "ext-xml": "*",
         "symfony/cache": "^5.2",
-        "symfony/config": "^5.0",
+        "symfony/config": "^5.3",
         "symfony/dependency-injection": "^5.3",
         "symfony/deprecation-contracts": "^2.1",
         "symfony/event-dispatcher": "^5.1",
@@ -30,7 +30,7 @@
         "symfony/polyfill-php80": "^1.15",
         "symfony/filesystem": "^4.4|^5.0",
         "symfony/finder": "^4.4|^5.0",
-        "symfony/routing": "^5.2"
+        "symfony/routing": "^5.3"
     },
     "require-dev": {
         "doctrine/annotations": "^1.10.4",
diff --git a/src/Symfony/Component/Config/Loader/FileLoader.php b/src/Symfony/Component/Config/Loader/FileLoader.php
index 0b01df49f3..4c2a43b14a 100644
--- a/src/Symfony/Component/Config/Loader/FileLoader.php
+++ b/src/Symfony/Component/Config/Loader/FileLoader.php
@@ -31,9 +31,10 @@ abstract class FileLoader extends Loader
 
     private $currentDir;
 
-    public function __construct(FileLocatorInterface $locator)
+    public function __construct(FileLocatorInterface $locator, string $env = null)
     {
         $this->locator = $locator;
+        parent::__construct($env);
     }
 
     /**
diff --git a/src/Symfony/Component/Config/Loader/Loader.php b/src/Symfony/Component/Config/Loader/Loader.php
index 62cae685e2..92b894f7d8 100644
--- a/src/Symfony/Component/Config/Loader/Loader.php
+++ b/src/Symfony/Component/Config/Loader/Loader.php
@@ -21,6 +21,12 @@ use Symfony\Component\Config\Exception\LoaderLoadException;
 abstract class Loader implements LoaderInterface
 {
     protected $resolver;
+    protected $env;
+
+    public function __construct(string $env = null)
+    {
+        $this->env = $env;
+    }
 
     /**
      * {@inheritdoc}
diff --git a/src/Symfony/Component/DependencyInjection/CHANGELOG.md b/src/Symfony/Component/DependencyInjection/CHANGELOG.md
index a6c60db0e2..c08e7cb75d 100644
--- a/src/Symfony/Component/DependencyInjection/CHANGELOG.md
+++ b/src/Symfony/Component/DependencyInjection/CHANGELOG.md
@@ -8,6 +8,7 @@ CHANGELOG
  * Add `%env(not:...)%` processor to negate boolean values
  * Add support for loading autoconfiguration rules via the `#[Autoconfigure]` and `#[AutoconfigureTag]` attributes on PHP 8
  * Add autoconfigurable attributes
+ * Add support for per-env configuration in loaders
 
 5.2.0
 -----
diff --git a/src/Symfony/Component/DependencyInjection/Loader/ClosureLoader.php b/src/Symfony/Component/DependencyInjection/Loader/ClosureLoader.php
index 57aa83d6a0..a8337d4e66 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/ClosureLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/ClosureLoader.php
@@ -25,9 +25,10 @@ class ClosureLoader extends Loader
 {
     private $container;
 
-    public function __construct(ContainerBuilder $container)
+    public function __construct(ContainerBuilder $container, string $env = null)
     {
         $this->container = $container;
+        parent::__construct($env);
     }
 
     /**
@@ -35,7 +36,7 @@ class ClosureLoader extends Loader
      */
     public function load($resource, string $type = null)
     {
-        $resource($this->container);
+        $resource($this->container, $this->env);
     }
 
     /**
diff --git a/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php b/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php
index 7c4377f7aa..5fc8f5b6c8 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/Configurator/ContainerConfigurator.php
@@ -35,14 +35,16 @@ class ContainerConfigurator extends AbstractConfigurator
     private $path;
     private $file;
     private $anonymousCount = 0;
+    private $env;
 
-    public function __construct(ContainerBuilder $container, PhpFileLoader $loader, array &$instanceof, string $path, string $file)
+    public function __construct(ContainerBuilder $container, PhpFileLoader $loader, array &$instanceof, string $path, string $file, string $env = null)
     {
         $this->container = $container;
         $this->loader = $loader;
         $this->instanceof = &$instanceof;
         $this->path = $path;
         $this->file = $file;
+        $this->env = $env;
     }
 
     final public function extension(string $namespace, array $config)
@@ -71,6 +73,23 @@ class ContainerConfigurator extends AbstractConfigurator
         return new ServicesConfigurator($this->container, $this->loader, $this->instanceof, $this->path, $this->anonymousCount);
     }
 
+    /**
+     * @return static
+     */
+    final public function when(string $env): self
+    {
+        if ($env === $this->env) {
+            return clone $this;
+        }
+
+        $instanceof = $this->instanceof;
+        $clone = clone $this;
+        $clone->container = new ContainerBuilder(clone $this->container->getParameterBag());
+        $clone->instanceof = &$instanceof;
+
+        return $clone;
+    }
+
     /**
      * @return static
      */
diff --git a/src/Symfony/Component/DependencyInjection/Loader/FileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/FileLoader.php
index b0d3e952e9..75606c5abf 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/FileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/FileLoader.php
@@ -39,11 +39,11 @@ abstract class FileLoader extends BaseFileLoader
     protected $singlyImplemented = [];
     protected $autoRegisterAliasesForSinglyImplementedInterfaces = true;
 
-    public function __construct(ContainerBuilder $container, FileLocatorInterface $locator)
+    public function __construct(ContainerBuilder $container, FileLocatorInterface $locator, string $env = null)
     {
         $this->container = $container;
 
-        parent::__construct($locator);
+        parent::__construct($locator, $env);
     }
 
     /**
diff --git a/src/Symfony/Component/DependencyInjection/Loader/IniFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/IniFileLoader.php
index f313cbcae4..fbf313878b 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/IniFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/IniFileLoader.php
@@ -44,6 +44,12 @@ class IniFileLoader extends FileLoader
                 $this->container->setParameter($key, $this->phpize($value));
             }
         }
+
+        if ($this->env && \is_array($result['parameters@'.$this->env] ?? null)) {
+            foreach ($result['parameters@'.$this->env] as $key => $value) {
+                $this->container->setParameter($key, $this->phpize($value));
+            }
+        }
     }
 
     /**
diff --git a/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php
index 5c7b628eab..130d7cfba7 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/PhpFileLoader.php
@@ -47,7 +47,7 @@ class PhpFileLoader extends FileLoader
             $callback = $load($path);
 
             if (\is_object($callback) && \is_callable($callback)) {
-                $callback(new ContainerConfigurator($this->container, $this, $this->instanceof, $path, $resource), $this->container, $this);
+                $callback(new ContainerConfigurator($this->container, $this, $this->instanceof, $path, $resource, $this->env), $this->container, $this);
             }
         } finally {
             $this->instanceof = [];
diff --git a/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
index a5b42f8835..b694b7791c 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php
@@ -50,23 +50,36 @@ class XmlFileLoader extends FileLoader
 
         $this->container->fileExists($path);
 
-        $defaults = $this->getServiceDefaults($xml, $path);
+        $this->loadXml($xml, $path);
+
+        if ($this->env) {
+            $xpath = new \DOMXPath($xml);
+            $xpath->registerNamespace('container', self::NS);
+            foreach ($xpath->query(sprintf('//container:when[@env="%s"]', $this->env)) ?: [] as $root) {
+                $this->loadXml($xml, $path, $root);
+            }
+        }
+    }
+
+    private function loadXml(\DOMDocument $xml, string $path, \DOMNode $root = null): void
+    {
+        $defaults = $this->getServiceDefaults($xml, $path, $root);
 
         // anonymous services
-        $this->processAnonymousServices($xml, $path);
+        $this->processAnonymousServices($xml, $path, $root);
 
         // imports
-        $this->parseImports($xml, $path);
+        $this->parseImports($xml, $path, $root);
 
         // parameters
-        $this->parseParameters($xml, $path);
+        $this->parseParameters($xml, $path, $root);
 
         // extensions
-        $this->loadFromExtensions($xml);
+        $this->loadFromExtensions($xml, $root);
 
         // services
         try {
-            $this->parseDefinitions($xml, $path, $defaults);
+            $this->parseDefinitions($xml, $path, $defaults, $root);
         } finally {
             $this->instanceof = [];
             $this->registerAliasesForSinglyImplementedInterfaces();
@@ -89,19 +102,19 @@ class XmlFileLoader extends FileLoader
         return 'xml' === $type;
     }
 
-    private function parseParameters(\DOMDocument $xml, string $file)
+    private function parseParameters(\DOMDocument $xml, string $file, \DOMNode $root = null)
     {
-        if ($parameters = $this->getChildren($xml->documentElement, 'parameters')) {
+        if ($parameters = $this->getChildren($root ?? $xml->documentElement, 'parameters')) {
             $this->container->getParameterBag()->add($this->getArgumentsAsPhp($parameters[0], 'parameter', $file));
         }
     }
 
-    private function parseImports(\DOMDocument $xml, string $file)
+    private function parseImports(\DOMDocument $xml, string $file, \DOMNode $root = null)
     {
         $xpath = new \DOMXPath($xml);
         $xpath->registerNamespace('container', self::NS);
 
-        if (false === $imports = $xpath->query('//container:imports/container:import')) {
+        if (false === $imports = $xpath->query('.//container:imports/container:import', $root)) {
             return;
         }
 
@@ -112,19 +125,19 @@ class XmlFileLoader extends FileLoader
         }
     }
 
-    private function parseDefinitions(\DOMDocument $xml, string $file, Definition $defaults)
+    private function parseDefinitions(\DOMDocument $xml, string $file, Definition $defaults, \DOMNode $root = null)
     {
         $xpath = new \DOMXPath($xml);
         $xpath->registerNamespace('container', self::NS);
 
-        if (false === $services = $xpath->query('//container:services/container:service|//container:services/container:prototype|//container:services/container:stack')) {
+        if (false === $services = $xpath->query('.//container:services/container:service|.//container:services/container:prototype|.//container:services/container:stack', $root)) {
             return;
         }
         $this->setCurrentDir(\dirname($file));
 
         $this->instanceof = [];
         $this->isLoadingInstanceof = true;
-        $instanceof = $xpath->query('//container:services/container:instanceof');
+        $instanceof = $xpath->query('.//container:services/container:instanceof', $root);
         foreach ($instanceof as $service) {
             $this->setDefinition((string) $service->getAttribute('id'), $this->parseDefinition($service, $file, new Definition()));
         }
@@ -170,12 +183,12 @@ class XmlFileLoader extends FileLoader
         }
     }
 
-    private function getServiceDefaults(\DOMDocument $xml, string $file): Definition
+    private function getServiceDefaults(\DOMDocument $xml, string $file, \DOMNode $root = null): Definition
     {
         $xpath = new \DOMXPath($xml);
         $xpath->registerNamespace('container', self::NS);
 
-        if (null === $defaultsNode = $xpath->query('//container:services/container:defaults')->item(0)) {
+        if (null === $defaultsNode = $xpath->query('.//container:services/container:defaults', $root)->item(0)) {
             return new Definition();
         }
 
@@ -393,7 +406,7 @@ class XmlFileLoader extends FileLoader
     /**
      * Processes anonymous services.
      */
-    private function processAnonymousServices(\DOMDocument $xml, string $file)
+    private function processAnonymousServices(\DOMDocument $xml, string $file, \DOMNode $root = null)
     {
         $definitions = [];
         $count = 0;
@@ -403,7 +416,7 @@ class XmlFileLoader extends FileLoader
         $xpath->registerNamespace('container', self::NS);
 
         // anonymous services as arguments/properties
-        if (false !== $nodes = $xpath->query('//container:argument[@type="service"][not(@id)]|//container:property[@type="service"][not(@id)]|//container:bind[not(@id)]|//container:factory[not(@service)]|//container:configurator[not(@service)]')) {
+        if (false !== $nodes = $xpath->query('.//container:argument[@type="service"][not(@id)]|.//container:property[@type="service"][not(@id)]|.//container:bind[not(@id)]|.//container:factory[not(@service)]|.//container:configurator[not(@service)]', $root)) {
             foreach ($nodes as $node) {
                 if ($services = $this->getChildren($node, 'service')) {
                     // give it a unique name
@@ -422,7 +435,7 @@ class XmlFileLoader extends FileLoader
         }
 
         // anonymous services "in the wild"
-        if (false !== $nodes = $xpath->query('//container:services/container:service[not(@id)]')) {
+        if (false !== $nodes = $xpath->query('.//container:services/container:service[not(@id)]', $root)) {
             foreach ($nodes as $node) {
                 throw new InvalidArgumentException(sprintf('Top-level services must have "id" attribute, none found in "%s" at line %d.', $file, $node->getLineNo()));
             }
diff --git a/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
index 22f029cca8..530f88d4b5 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php
@@ -129,6 +129,20 @@ class YamlFileLoader extends FileLoader
             return;
         }
 
+        $this->loadContent($content, $path);
+
+        // per-env configuration
+        if ($this->env && isset($content['when@'.$this->env])) {
+            if (!\is_array($content['when@'.$this->env])) {
+                throw new InvalidArgumentException(sprintf('The "when@%s" key should contain an array in "%s". Check your YAML syntax.', $this->env, $path));
+            }
+
+            $this->loadContent($content['when@'.$this->env], $path);
+        }
+    }
+
+    private function loadContent($content, $path)
+    {
         // imports
         $this->parseImports($content, $path);
 
@@ -770,7 +784,7 @@ class YamlFileLoader extends FileLoader
         }
 
         foreach ($content as $namespace => $data) {
-            if (\in_array($namespace, ['imports', 'parameters', 'services'])) {
+            if (\in_array($namespace, ['imports', 'parameters', 'services']) || 0 === strpos($namespace, 'when@')) {
                 continue;
             }
 
@@ -907,7 +921,7 @@ class YamlFileLoader extends FileLoader
     private function loadFromExtensions(array $content)
     {
         foreach ($content as $namespace => $values) {
-            if (\in_array($namespace, ['imports', 'parameters', 'services'])) {
+            if (\in_array($namespace, ['imports', 'parameters', 'services']) || 0 === strpos($namespace, 'when@')) {
                 continue;
             }
 
diff --git a/src/Symfony/Component/DependencyInjection/Loader/schema/dic/services/services-1.0.xsd b/src/Symfony/Component/DependencyInjection/Loader/schema/dic/services/services-1.0.xsd
index 03988686ba..f295f7e6f7 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/schema/dic/services/services-1.0.xsd
+++ b/src/Symfony/Component/DependencyInjection/Loader/schema/dic/services/services-1.0.xsd
@@ -37,9 +37,31 @@
         <xsd:element name="services" type="services" />
         <xsd:group ref="foreign" />
       </xsd:sequence>
+      <xsd:sequence minOccurs="0" maxOccurs="unbounded">
+        <xsd:element name="when" type="when" />
+      </xsd:sequence>
     </xsd:sequence>
   </xsd:complexType>
 
+  <xsd:complexType name="when">
+    <xsd:sequence>
+      <xsd:group ref="foreign" />
+      <xsd:sequence minOccurs="0">
+        <xsd:element name="imports" type="imports" />
+        <xsd:group ref="foreign" />
+      </xsd:sequence>
+      <xsd:sequence minOccurs="0">
+        <xsd:element name="parameters" type="parameters" />
+        <xsd:group ref="foreign" />
+      </xsd:sequence>
+      <xsd:sequence minOccurs="0">
+        <xsd:element name="services" type="services" />
+        <xsd:group ref="foreign" />
+      </xsd:sequence>
+    </xsd:sequence>
+    <xsd:attribute name="env" type="xsd:string" use="required" />
+  </xsd:complexType>
+
   <xsd:group name="foreign">
     <xsd:sequence>
       <xsd:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded" />
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/config/when-env.php b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/config/when-env.php
new file mode 100644
index 0000000000..5170261ad8
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/config/when-env.php
@@ -0,0 +1,20 @@
+<?php
+
+namespace Symfony\Component\DependencyInjection\Loader\Configurator;
+
+use App\BarService;
+
+return function (ContainerConfigurator $c) {
+    $c->parameters()
+        ->set('foo', 123);
+
+    $c->when('some-env')
+        ->parameters()
+            ->set('foo', 234)
+            ->set('bar', 345);
+
+    $c->when('some-other-env')
+        ->parameters()
+            ->set('foo', 456)
+            ->set('baz', 567);
+};
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/ini/when-env.ini b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/ini/when-env.ini
new file mode 100644
index 0000000000..053fe86f86
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/ini/when-env.ini
@@ -0,0 +1,10 @@
+[parameters@some-env]
+    foo = 234
+    bar = 345
+
+[parameters@some-other-env]
+    foo = 456
+    baz = 567
+
+[parameters]
+    foo = 123
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/when-env.xml b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/when-env.xml
new file mode 100644
index 0000000000..1d12221a2f
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/xml/when-env.xml
@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="utf-8"?>
+<container xmlns="http://symfony.com/schema/dic/services" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://symfony.com/schema/dic/services https://symfony.com/schema/dic/services/services-1.0.xsd">
+    <parameters>
+        <parameter key="foo">123</parameter>
+    </parameters>
+    <when env="some-env">
+        <parameters>
+            <parameter key="foo">234</parameter>
+            <parameter key="bar">345</parameter>
+        </parameters>
+    </when>
+    <when env="some-other-env">
+        <parameters>
+            <parameter key="foo">456</parameter>
+            <parameter key="baz">567</parameter>
+        </parameters>
+    </when>
+</container>
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/when-env.yaml b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/when-env.yaml
new file mode 100644
index 0000000000..22590d9b80
--- /dev/null
+++ b/src/Symfony/Component/DependencyInjection/Tests/Fixtures/yaml/when-env.yaml
@@ -0,0 +1,12 @@
+when@some-env:
+    parameters:
+        foo: 234
+        bar: 345
+
+when@some-other-env:
+    parameters:
+        foo: 456
+        baz: 567
+
+parameters:
+    foo: 123
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Loader/ClosureLoaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Loader/ClosureLoaderTest.php
index 125e09b6cf..a42ecf5a81 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Loader/ClosureLoaderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Loader/ClosureLoaderTest.php
@@ -27,12 +27,13 @@ class ClosureLoaderTest extends TestCase
 
     public function testLoad()
     {
-        $loader = new ClosureLoader($container = new ContainerBuilder());
+        $loader = new ClosureLoader($container = new ContainerBuilder(), 'some-env');
 
-        $loader->load(function ($container) {
+        $loader->load(function ($container, $env) {
             $container->setParameter('foo', 'foo');
+            $container->setParameter('env', $env);
         });
 
-        $this->assertEquals('foo', $container->getParameter('foo'), '->load() loads a \Closure resource');
+        $this->assertSame(['foo' => 'foo', 'env' => 'some-env'], $container->getParameterBag()->all());
     }
 }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Loader/IniFileLoaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Loader/IniFileLoaderTest.php
index b4cf503237..07f23f3137 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Loader/IniFileLoaderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Loader/IniFileLoaderTest.php
@@ -120,4 +120,13 @@ class IniFileLoaderTest extends TestCase
         $this->assertFalse($loader->supports('foo.foo'), '->supports() returns false if the resource is not loadable');
         $this->assertTrue($loader->supports('with_wrong_ext.yml', 'ini'), '->supports() returns true if the resource with forced type is loadable');
     }
+
+    public function testWhenEnv()
+    {
+        $container = new ContainerBuilder();
+        $loader = new IniFileLoader($container, new FileLocator(realpath(__DIR__.'/../Fixtures/').'/ini'), 'some-env');
+        $loader->load('when-env.ini');
+
+        $this->assertSame(['foo' => 234, 'bar' => 345], $container->getParameterBag()->all());
+    }
 }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Loader/PhpFileLoaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Loader/PhpFileLoaderTest.php
index bf53669cac..50f3c58dd8 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Loader/PhpFileLoaderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Loader/PhpFileLoaderTest.php
@@ -138,6 +138,15 @@ class PhpFileLoaderTest extends TestCase
         $this->assertEquals($expected, $container->get('stack_d'));
     }
 
+    public function testWhenEnv()
+    {
+        $container = new ContainerBuilder();
+        $loader = new PhpFileLoader($container, new FileLocator(realpath(__DIR__.'/../Fixtures').'/config'), 'some-env');
+        $loader->load('when-env.php');
+
+        $this->assertSame(['foo' => 234, 'bar' => 345], $container->getParameterBag()->all());
+    }
+
     /**
      * @group legacy
      */
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Loader/XmlFileLoaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Loader/XmlFileLoaderTest.php
index 8714905f71..1e446d0ada 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Loader/XmlFileLoaderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Loader/XmlFileLoaderTest.php
@@ -1083,4 +1083,13 @@ class XmlFileLoaderTest extends TestCase
         $expected->label = 'Z';
         $this->assertEquals($expected, $container->get('stack_d'));
     }
+
+    public function testWhenEnv()
+    {
+        $container = new ContainerBuilder();
+        $loader = new XmlFileLoader($container, new FileLocator(self::$fixturesPath.'/xml'), 'some-env');
+        $loader->load('when-env.xml');
+
+        $this->assertSame(['foo' => 234, 'bar' => 345], $container->getParameterBag()->all());
+    }
 }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
index 508ecb8cb8..5c2b29559e 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Loader/YamlFileLoaderTest.php
@@ -1002,4 +1002,13 @@ class YamlFileLoaderTest extends TestCase
         ];
         $this->assertEquals($expected, $container->get('stack_e'));
     }
+
+    public function testWhenEnv()
+    {
+        $container = new ContainerBuilder();
+        $loader = new YamlFileLoader($container, new FileLocator(self::$fixturesPath.'/yaml'), 'some-env');
+        $loader->load('when-env.yaml');
+
+        $this->assertSame(['foo' => 234, 'bar' => 345], $container->getParameterBag()->all());
+    }
 }
diff --git a/src/Symfony/Component/DependencyInjection/composer.json b/src/Symfony/Component/DependencyInjection/composer.json
index c5752e46d0..efec2a3bc3 100644
--- a/src/Symfony/Component/DependencyInjection/composer.json
+++ b/src/Symfony/Component/DependencyInjection/composer.json
@@ -24,7 +24,7 @@
     },
     "require-dev": {
         "symfony/yaml": "^4.4|^5.0",
-        "symfony/config": "^5.1",
+        "symfony/config": "^5.3",
         "symfony/expression-language": "^4.4|^5.0"
     },
     "suggest": {
@@ -35,7 +35,7 @@
         "symfony/proxy-manager-bridge": "Generate service proxies to lazy load them"
     },
     "conflict": {
-        "symfony/config": "<5.1",
+        "symfony/config": "<5.3",
         "symfony/finder": "<4.4",
         "symfony/proxy-manager-bridge": "<4.4",
         "symfony/yaml": "<4.4"
diff --git a/src/Symfony/Component/HttpKernel/Kernel.php b/src/Symfony/Component/HttpKernel/Kernel.php
index 5ecad3b9a9..ad6a7e1ec0 100644
--- a/src/Symfony/Component/HttpKernel/Kernel.php
+++ b/src/Symfony/Component/HttpKernel/Kernel.php
@@ -751,15 +751,16 @@ abstract class Kernel implements KernelInterface, RebootableInterface, Terminabl
      */
     protected function getContainerLoader(ContainerInterface $container)
     {
+        $env = $this->getEnvironment();
         $locator = new FileLocator($this);
         $resolver = new LoaderResolver([
-            new XmlFileLoader($container, $locator),
-            new YamlFileLoader($container, $locator),
-            new IniFileLoader($container, $locator),
-            new PhpFileLoader($container, $locator),
-            new GlobFileLoader($container, $locator),
-            new DirectoryLoader($container, $locator),
-            new ClosureLoader($container),
+            new XmlFileLoader($container, $locator, $env),
+            new YamlFileLoader($container, $locator, $env),
+            new IniFileLoader($container, $locator, $env),
+            new PhpFileLoader($container, $locator, $env),
+            new GlobFileLoader($container, $locator, $env),
+            new DirectoryLoader($container, $locator, $env),
+            new ClosureLoader($container, $env),
         ]);
 
         return new DelegatingLoader($resolver);
diff --git a/src/Symfony/Component/Routing/Annotation/Route.php b/src/Symfony/Component/Routing/Annotation/Route.php
index f51b74c387..418887da26 100644
--- a/src/Symfony/Component/Routing/Annotation/Route.php
+++ b/src/Symfony/Component/Routing/Annotation/Route.php
@@ -34,6 +34,7 @@ class Route
     private $schemes = [];
     private $condition;
     private $priority;
+    private $env;
 
     /**
      * @param array|string      $data         data array managed by the Doctrine Annotations library or the path
@@ -59,7 +60,8 @@ class Route
         string $locale = null,
         string $format = null,
         bool $utf8 = null,
-        bool $stateless = null
+        bool $stateless = null,
+        string $env = null
     ) {
         if (\is_string($data)) {
             $data = ['path' => $data];
@@ -84,6 +86,7 @@ class Route
         $data['format'] = $data['format'] ?? $format;
         $data['utf8'] = $data['utf8'] ?? $utf8;
         $data['stateless'] = $data['stateless'] ?? $stateless;
+        $data['env'] = $data['env'] ?? $env;
 
         $data = array_filter($data, static function ($value): bool {
             return null !== $value;
@@ -241,4 +244,14 @@ class Route
     {
         return $this->priority;
     }
+
+    public function setEnv(?string $env): void
+    {
+        $this->env = $env;
+    }
+
+    public function getEnv(): ?string
+    {
+        return $this->env;
+    }
 }
diff --git a/src/Symfony/Component/Routing/CHANGELOG.md b/src/Symfony/Component/Routing/CHANGELOG.md
index 840df13441..b664e03aea 100644
--- a/src/Symfony/Component/Routing/CHANGELOG.md
+++ b/src/Symfony/Component/Routing/CHANGELOG.md
@@ -1,10 +1,11 @@
 CHANGELOG
 =========
 
-5.3.0
------
+5.3
+---
 
- * already encoded slashes are not decoded nor double-encoded anymore when generating URLs
+ * Already encoded slashes are not decoded nor double-encoded anymore when generating URLs
+ * Add support for per-env configuration in loaders
 
 5.2.0
 -----
diff --git a/src/Symfony/Component/Routing/Loader/AnnotationClassLoader.php b/src/Symfony/Component/Routing/Loader/AnnotationClassLoader.php
index bf8fe2af36..0b362ad1e0 100644
--- a/src/Symfony/Component/Routing/Loader/AnnotationClassLoader.php
+++ b/src/Symfony/Component/Routing/Loader/AnnotationClassLoader.php
@@ -73,6 +73,7 @@ use Symfony\Component\Routing\RouteCollection;
 abstract class AnnotationClassLoader implements LoaderInterface
 {
     protected $reader;
+    protected $env;
 
     /**
      * @var string
@@ -84,9 +85,10 @@ abstract class AnnotationClassLoader implements LoaderInterface
      */
     protected $defaultRouteIndex = 0;
 
-    public function __construct(Reader $reader = null)
+    public function __construct(Reader $reader = null, string $env = null)
     {
         $this->reader = $reader;
+        $this->env = $env;
     }
 
     /**
@@ -122,6 +124,10 @@ abstract class AnnotationClassLoader implements LoaderInterface
         $collection = new RouteCollection();
         $collection->addResource(new FileResource($class->getFileName()));
 
+        if ($globals['env'] && $this->env !== $globals['env']) {
+            return $collection;
+        }
+
         foreach ($class->getMethods() as $method) {
             $this->defaultRouteIndex = 0;
             foreach ($this->getAnnotations($method) as $annot) {
@@ -144,6 +150,10 @@ abstract class AnnotationClassLoader implements LoaderInterface
      */
     protected function addRoute(RouteCollection $collection, object $annot, array $globals, \ReflectionClass $class, \ReflectionMethod $method)
     {
+        if ($annot->getEnv() && $annot->getEnv() !== $this->env) {
+            return;
+        }
+
         $name = $annot->getName();
         if (null === $name) {
             $name = $this->getDefaultRouteName($class, $method);
@@ -317,6 +327,7 @@ abstract class AnnotationClassLoader implements LoaderInterface
             }
 
             $globals['priority'] = $annot->getPriority() ?? 0;
+            $globals['env'] = $annot->getEnv();
 
             foreach ($globals['requirements'] as $placeholder => $requirement) {
                 if (\is_int($placeholder)) {
@@ -342,6 +353,7 @@ abstract class AnnotationClassLoader implements LoaderInterface
             'condition' => '',
             'name' => '',
             'priority' => 0,
+            'env' => null,
         ];
     }
 
diff --git a/src/Symfony/Component/Routing/Loader/ClosureLoader.php b/src/Symfony/Component/Routing/Loader/ClosureLoader.php
index cea5f9c194..2407307482 100644
--- a/src/Symfony/Component/Routing/Loader/ClosureLoader.php
+++ b/src/Symfony/Component/Routing/Loader/ClosureLoader.php
@@ -33,7 +33,7 @@ class ClosureLoader extends Loader
      */
     public function load($closure, string $type = null)
     {
-        return $closure();
+        return $closure($this->env);
     }
 
     /**
diff --git a/src/Symfony/Component/Routing/Loader/Configurator/RoutingConfigurator.php b/src/Symfony/Component/Routing/Loader/Configurator/RoutingConfigurator.php
index e5086e2441..70d68dfc3c 100644
--- a/src/Symfony/Component/Routing/Loader/Configurator/RoutingConfigurator.php
+++ b/src/Symfony/Component/Routing/Loader/Configurator/RoutingConfigurator.php
@@ -24,13 +24,15 @@ class RoutingConfigurator
     private $loader;
     private $path;
     private $file;
+    private $env;
 
-    public function __construct(RouteCollection $collection, PhpFileLoader $loader, string $path, string $file)
+    public function __construct(RouteCollection $collection, PhpFileLoader $loader, string $path, string $file, string $env = null)
     {
         $this->collection = $collection;
         $this->loader = $loader;
         $this->path = $path;
         $this->file = $file;
+        $this->env = $env;
     }
 
     /**
@@ -58,6 +60,21 @@ class RoutingConfigurator
         return new CollectionConfigurator($this->collection, $name);
     }
 
+    /**
+     * @return static
+     */
+    final public function when(string $env): self
+    {
+        if ($env === $this->env) {
+            return clone $this;
+        }
+
+        $clone = clone $this;
+        $clone->collection = new RouteCollection();
+
+        return $clone;
+    }
+
     /**
      * @return static
      */
diff --git a/src/Symfony/Component/Routing/Loader/ContainerLoader.php b/src/Symfony/Component/Routing/Loader/ContainerLoader.php
index 92bf2a096b..8128b74213 100644
--- a/src/Symfony/Component/Routing/Loader/ContainerLoader.php
+++ b/src/Symfony/Component/Routing/Loader/ContainerLoader.php
@@ -22,9 +22,10 @@ class ContainerLoader extends ObjectLoader
 {
     private $container;
 
-    public function __construct(ContainerInterface $container)
+    public function __construct(ContainerInterface $container, string $env = null)
     {
         $this->container = $container;
+        parent::__construct($env);
     }
 
     /**
diff --git a/src/Symfony/Component/Routing/Loader/ObjectLoader.php b/src/Symfony/Component/Routing/Loader/ObjectLoader.php
index d6ec1a7277..062453908c 100644
--- a/src/Symfony/Component/Routing/Loader/ObjectLoader.php
+++ b/src/Symfony/Component/Routing/Loader/ObjectLoader.php
@@ -59,7 +59,7 @@ abstract class ObjectLoader extends Loader
             throw new \BadMethodCallException(sprintf('Method "%s" not found on "%s" when importing routing resource "%s".', $method, get_debug_type($loaderObject), $resource));
         }
 
-        $routeCollection = $loaderObject->$method($this);
+        $routeCollection = $loaderObject->$method($this, $this->env);
 
         if (!$routeCollection instanceof RouteCollection) {
             $type = get_debug_type($routeCollection);
diff --git a/src/Symfony/Component/Routing/Loader/PhpFileLoader.php b/src/Symfony/Component/Routing/Loader/PhpFileLoader.php
index e000c5a0eb..2418b0d322 100644
--- a/src/Symfony/Component/Routing/Loader/PhpFileLoader.php
+++ b/src/Symfony/Component/Routing/Loader/PhpFileLoader.php
@@ -71,7 +71,7 @@ class PhpFileLoader extends FileLoader
     {
         $collection = new RouteCollection();
 
-        $result(new RoutingConfigurator($collection, $this, $path, $file));
+        $result(new RoutingConfigurator($collection, $this, $path, $file, $this->env));
 
         return $collection;
     }
diff --git a/src/Symfony/Component/Routing/Loader/XmlFileLoader.php b/src/Symfony/Component/Routing/Loader/XmlFileLoader.php
index 9951625be9..4f38ce95cc 100644
--- a/src/Symfony/Component/Routing/Loader/XmlFileLoader.php
+++ b/src/Symfony/Component/Routing/Loader/XmlFileLoader.php
@@ -88,6 +88,16 @@ class XmlFileLoader extends FileLoader
             case 'import':
                 $this->parseImport($collection, $node, $path, $file);
                 break;
+            case 'when':
+                if (!$this->env || $node->getAttribute('env') !== $this->env) {
+                    break;
+                }
+                foreach ($node->childNodes as $node) {
+                    if ($node instanceof \DOMElement) {
+                        $this->parseNode($collection, $node, $path, $file);
+                    }
+                }
+                break;
             default:
                 throw new \InvalidArgumentException(sprintf('Unknown tag "%s" used in file "%s". Expected "route" or "import".', $node->localName, $path));
         }
diff --git a/src/Symfony/Component/Routing/Loader/YamlFileLoader.php b/src/Symfony/Component/Routing/Loader/YamlFileLoader.php
index b236e4b54e..1ec8a810a2 100644
--- a/src/Symfony/Component/Routing/Loader/YamlFileLoader.php
+++ b/src/Symfony/Component/Routing/Loader/YamlFileLoader.php
@@ -84,6 +84,24 @@ class YamlFileLoader extends FileLoader
         }
 
         foreach ($parsedConfig as $name => $config) {
+            if (0 === strpos($name, 'when@')) {
+                if (!$this->env || 'when@'.$this->env !== $name) {
+                    continue;
+                }
+
+                foreach ($config as $name => $config) {
+                    $this->validate($config, $name.'" when "@'.$this->env, $path);
+
+                    if (isset($config['resource'])) {
+                        $this->parseImport($collection, $config, $path, $file);
+                    } else {
+                        $this->parseRoute($collection, $name, $config, $path);
+                    }
+                }
+
+                continue;
+            }
+
             $this->validate($config, $name, $path);
 
             if (isset($config['resource'])) {
diff --git a/src/Symfony/Component/Routing/Loader/schema/routing/routing-1.0.xsd b/src/Symfony/Component/Routing/Loader/schema/routing/routing-1.0.xsd
index 846d126724..e03114791e 100644
--- a/src/Symfony/Component/Routing/Loader/schema/routing/routing-1.0.xsd
+++ b/src/Symfony/Component/Routing/Loader/schema/routing/routing-1.0.xsd
@@ -21,9 +21,18 @@
     <xsd:choice minOccurs="0" maxOccurs="unbounded">
       <xsd:element name="import" type="import" />
       <xsd:element name="route" type="route" />
+      <xsd:element name="when" type="when" />
     </xsd:choice>
   </xsd:complexType>
 
+  <xsd:complexType name="when">
+    <xsd:choice minOccurs="0" maxOccurs="unbounded">
+      <xsd:element name="import" type="import" />
+      <xsd:element name="route" type="route" />
+    </xsd:choice>
+    <xsd:attribute name="env" type="xsd:string" use="required" />
+  </xsd:complexType>
+
   <xsd:complexType name="localized-path">
     <xsd:simpleContent>
       <xsd:extension base="xsd:string">
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/AnnotationFixtures/RouteWithEnv.php b/src/Symfony/Component/Routing/Tests/Fixtures/AnnotationFixtures/RouteWithEnv.php
new file mode 100644
index 0000000000..dcc94e7a17
--- /dev/null
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/AnnotationFixtures/RouteWithEnv.php
@@ -0,0 +1,25 @@
+<?php
+
+namespace Symfony\Component\Routing\Tests\Fixtures\AnnotationFixtures;
+
+use Symfony\Component\Routing\Annotation\Route;
+
+/**
+ * @Route(env="some-env")
+ */
+class RouteWithEnv
+{
+    /**
+     * @Route("/path", name="action")
+     */
+    public function action()
+    {
+    }
+
+    /**
+     * @Route("/path2", name="action2", env="some-other-env")
+     */
+    public function action2()
+    {
+    }
+}
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/AttributeFixtures/RouteWithEnv.php b/src/Symfony/Component/Routing/Tests/Fixtures/AttributeFixtures/RouteWithEnv.php
new file mode 100644
index 0000000000..e82a8136ba
--- /dev/null
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/AttributeFixtures/RouteWithEnv.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace Symfony\Component\Routing\Tests\Fixtures\AttributeFixtures;
+
+use Symfony\Component\Routing\Annotation\Route;
+
+#[Route(env: 'some-env')]
+class RouteWithEnv
+{
+    #[Route(path: '/path', name: 'action')]
+    public function action()
+    {
+    }
+
+    #[Route(path: '/path2', name: 'action2', env: 'some-other-env')]
+    public function action2()
+    {
+    }
+}
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/when-env.php b/src/Symfony/Component/Routing/Tests/Fixtures/when-env.php
new file mode 100644
index 0000000000..b52a629261
--- /dev/null
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/when-env.php
@@ -0,0 +1,18 @@
+<?php
+
+namespace Symfony\Component\Routing\Loader\Configurator;
+
+return function (RoutingConfigurator $routes) {
+    $routes
+        ->when('some-env')
+            ->add('a', '/a2')
+            ->add('b', '/b');
+
+    $routes
+        ->when('some-other-env')
+            ->add('a', '/a3')
+            ->add('c', '/c');
+
+    $routes
+        ->add('a', '/a1');
+};
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/when-env.xml b/src/Symfony/Component/Routing/Tests/Fixtures/when-env.xml
new file mode 100644
index 0000000000..50d1fd8b39
--- /dev/null
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/when-env.xml
@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<routes xmlns="http://symfony.com/schema/routing"
+        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:schemaLocation="http://symfony.com/schema/routing
+        https://symfony.com/schema/routing/routing-1.0.xsd">
+    <when env="some-env">
+        <route id="a" path="/a2" />
+        <route id="b" path="/b" />
+    </when>
+
+    <when env="some-other-env">
+        <route id="a" path="/a3" />
+        <route id="c" path="/c" />
+    </when>
+
+    <route id="a" path="/a1" />
+</routes>
diff --git a/src/Symfony/Component/Routing/Tests/Fixtures/when-env.yml b/src/Symfony/Component/Routing/Tests/Fixtures/when-env.yml
new file mode 100644
index 0000000000..0f97ab22f2
--- /dev/null
+++ b/src/Symfony/Component/Routing/Tests/Fixtures/when-env.yml
@@ -0,0 +1,9 @@
+when@some-env:
+    a: {path: /a2}
+    b: {path: /b}
+
+when@some-other-env:
+    a: {path: /a3}
+    c: {path: /c}
+
+a: {path: /a1}
diff --git a/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderTest.php b/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderTest.php
index 3b82499c4f..a4f6e3e3a6 100644
--- a/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderTest.php
+++ b/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderTest.php
@@ -247,5 +247,16 @@ abstract class AnnotationClassLoaderTest extends TestCase
         $this->assertEquals('/prefix/path', $routes->get('action')->getPath());
     }
 
+    public function testWhenEnv()
+    {
+        $routes = $this->loader->load($this->getNamespace().'\RouteWithEnv');
+        $this->assertCount(0, $routes);
+
+        $this->setUp('some-env');
+        $routes = $this->loader->load($this->getNamespace().'\RouteWithEnv');
+        $this->assertCount(1, $routes);
+        $this->assertSame('/path', $routes->get('action')->getPath());
+    }
+
     abstract protected function getNamespace(): string;
 }
diff --git a/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderWithAnnotationsTest.php b/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderWithAnnotationsTest.php
index ef9ca39e82..d2fe627ef9 100644
--- a/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderWithAnnotationsTest.php
+++ b/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderWithAnnotationsTest.php
@@ -9,10 +9,10 @@ use Symfony\Component\Routing\Route;
 
 class AnnotationClassLoaderWithAnnotationsTest extends AnnotationClassLoaderTest
 {
-    protected function setUp(): void
+    protected function setUp(string $env = null): void
     {
         $reader = new AnnotationReader();
-        $this->loader = new class($reader) extends AnnotationClassLoader {
+        $this->loader = new class($reader, $env) extends AnnotationClassLoader {
             protected function configureRoute(Route $route, \ReflectionClass $class, \ReflectionMethod $method, object $annot): void
             {
             }
diff --git a/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderWithAttributesTest.php b/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderWithAttributesTest.php
index 1545253e56..ea2a5c573b 100644
--- a/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderWithAttributesTest.php
+++ b/src/Symfony/Component/Routing/Tests/Loader/AnnotationClassLoaderWithAttributesTest.php
@@ -10,9 +10,9 @@ use Symfony\Component\Routing\Route;
  */
 class AnnotationClassLoaderWithAttributesTest extends AnnotationClassLoaderTest
 {
-    protected function setUp(): void
+    protected function setUp(string $env = null): void
     {
-        $this->loader = new class() extends AnnotationClassLoader {
+        $this->loader = new class(null, $env) extends AnnotationClassLoader {
             protected function configureRoute(Route $route, \ReflectionClass $class, \ReflectionMethod $method, object $annot): void
             {
             }
diff --git a/src/Symfony/Component/Routing/Tests/Loader/ClosureLoaderTest.php b/src/Symfony/Component/Routing/Tests/Loader/ClosureLoaderTest.php
index 5d963f86fb..da8ad090dd 100644
--- a/src/Symfony/Component/Routing/Tests/Loader/ClosureLoaderTest.php
+++ b/src/Symfony/Component/Routing/Tests/Loader/ClosureLoaderTest.php
@@ -33,10 +33,12 @@ class ClosureLoaderTest extends TestCase
 
     public function testLoad()
     {
-        $loader = new ClosureLoader();
+        $loader = new ClosureLoader('some-env');
 
         $route = new Route('/');
-        $routes = $loader->load(function () use ($route) {
+        $routes = $loader->load(function (string $env = null) use ($route) {
+            $this->assertSame('some-env', $env);
+
             $routes = new RouteCollection();
 
             $routes->add('foo', $route);
diff --git a/src/Symfony/Component/Routing/Tests/Loader/ObjectLoaderTest.php b/src/Symfony/Component/Routing/Tests/Loader/ObjectLoaderTest.php
index 50e75b5fd4..54d3643b1f 100644
--- a/src/Symfony/Component/Routing/Tests/Loader/ObjectLoaderTest.php
+++ b/src/Symfony/Component/Routing/Tests/Loader/ObjectLoaderTest.php
@@ -20,14 +20,14 @@ class ObjectLoaderTest extends TestCase
 {
     public function testLoadCallsServiceAndReturnsCollection()
     {
-        $loader = new TestObjectLoader();
+        $loader = new TestObjectLoader('some-env');
 
         // create a basic collection that will be returned
         $collection = new RouteCollection();
         $collection->add('foo', new Route('/foo'));
 
         $loader->loaderMap = [
-            'my_route_provider_service' => new TestObjectLoaderRouteService($collection),
+            'my_route_provider_service' => new TestObjectLoaderRouteService($collection, 'some-env'),
         ];
 
         $actualRoutes = $loader->load(
@@ -112,14 +112,20 @@ class TestObjectLoader extends ObjectLoader
 class TestObjectLoaderRouteService
 {
     private $collection;
+    private $env;
 
-    public function __construct($collection)
+    public function __construct($collection, string $env = null)
     {
         $this->collection = $collection;
+        $this->env = $env;
     }
 
-    public function loadRoutes()
+    public function loadRoutes(TestObjectLoader $loader, string $env = null)
     {
+        if ($this->env !== $env) {
+            throw new \InvalidArgumentException(sprintf('Expected env "%s", "%s" given.', $this->env, $env));
+        }
+
         return $this->collection;
     }
 }
diff --git a/src/Symfony/Component/Routing/Tests/Loader/PhpFileLoaderTest.php b/src/Symfony/Component/Routing/Tests/Loader/PhpFileLoaderTest.php
index 7ed941c711..fd3fca4154 100644
--- a/src/Symfony/Component/Routing/Tests/Loader/PhpFileLoaderTest.php
+++ b/src/Symfony/Component/Routing/Tests/Loader/PhpFileLoaderTest.php
@@ -284,4 +284,14 @@ class PhpFileLoaderTest extends TestCase
 
         $this->assertEquals($expectedRoutes('php'), $routes);
     }
+
+    public function testWhenEnv()
+    {
+        $loader = new PhpFileLoader(new FileLocator([__DIR__.'/../Fixtures']), 'some-env');
+        $routes = $loader->load('when-env.php');
+
+        $this->assertSame(['b', 'a'], array_keys($routes->all()));
+        $this->assertSame('/b', $routes->get('b')->getPath());
+        $this->assertSame('/a1', $routes->get('a')->getPath());
+    }
 }
diff --git a/src/Symfony/Component/Routing/Tests/Loader/XmlFileLoaderTest.php b/src/Symfony/Component/Routing/Tests/Loader/XmlFileLoaderTest.php
index 9ab49fc131..8518129a5b 100644
--- a/src/Symfony/Component/Routing/Tests/Loader/XmlFileLoaderTest.php
+++ b/src/Symfony/Component/Routing/Tests/Loader/XmlFileLoaderTest.php
@@ -563,4 +563,14 @@ class XmlFileLoaderTest extends TestCase
 
         $this->assertEquals($expectedRoutes('xml'), $routes);
     }
+
+    public function testWhenEnv()
+    {
+        $loader = new XmlFileLoader(new FileLocator([__DIR__.'/../Fixtures']), 'some-env');
+        $routes = $loader->load('when-env.xml');
+
+        $this->assertSame(['b', 'a'], array_keys($routes->all()));
+        $this->assertSame('/b', $routes->get('b')->getPath());
+        $this->assertSame('/a1', $routes->get('a')->getPath());
+    }
 }
diff --git a/src/Symfony/Component/Routing/Tests/Loader/YamlFileLoaderTest.php b/src/Symfony/Component/Routing/Tests/Loader/YamlFileLoaderTest.php
index 56915c5ce5..09e3f07951 100644
--- a/src/Symfony/Component/Routing/Tests/Loader/YamlFileLoaderTest.php
+++ b/src/Symfony/Component/Routing/Tests/Loader/YamlFileLoaderTest.php
@@ -435,4 +435,14 @@ class YamlFileLoaderTest extends TestCase
 
         $this->assertEquals($expectedRoutes('yml'), $routes);
     }
+
+    public function testWhenEnv()
+    {
+        $loader = new YamlFileLoader(new FileLocator([__DIR__.'/../Fixtures']), 'some-env');
+        $routes = $loader->load('when-env.yml');
+
+        $this->assertSame(['b', 'a'], array_keys($routes->all()));
+        $this->assertSame('/b', $routes->get('b')->getPath());
+        $this->assertSame('/a1', $routes->get('a')->getPath());
+    }
 }
diff --git a/src/Symfony/Component/Routing/composer.json b/src/Symfony/Component/Routing/composer.json
index 164dbb2bfd..11da29d649 100644
--- a/src/Symfony/Component/Routing/composer.json
+++ b/src/Symfony/Component/Routing/composer.json
@@ -21,7 +21,7 @@
         "symfony/polyfill-php80": "^1.15"
     },
     "require-dev": {
-        "symfony/config": "^5.0",
+        "symfony/config": "^5.3",
         "symfony/http-foundation": "^4.4|^5.0",
         "symfony/yaml": "^4.4|^5.0",
         "symfony/expression-language": "^4.4|^5.0",
@@ -30,7 +30,7 @@
         "psr/log": "~1.0"
     },
     "conflict": {
-        "symfony/config": "<5.0",
+        "symfony/config": "<5.3",
         "symfony/dependency-injection": "<4.4",
         "symfony/yaml": "<4.4"
     },