diff --git a/UPGRADE-5.1.md b/UPGRADE-5.1.md
index 96c1c8b0e2d90..bb8eda0b7e470 100644
--- a/UPGRADE-5.1.md
+++ b/UPGRADE-5.1.md
@@ -39,6 +39,11 @@ HttpFoundation
    `__construct()` instead)
  * Made the Mime component an optional dependency
 
+HttpKernel
+----------
+
+ * Deprecated support for `service:action` syntax to reference controllers. Use `serviceOrFqcn::method` instead.
+
 Mailer
 ------
 
diff --git a/UPGRADE-6.0.md b/UPGRADE-6.0.md
index 4180954165f54..08b811e1ecd57 100644
--- a/UPGRADE-6.0.md
+++ b/UPGRADE-6.0.md
@@ -36,6 +36,11 @@ HttpFoundation
    `RedirectResponse::create()`, and `StreamedResponse::create()` methods (use
    `__construct()` instead)
 
+HttpKernel
+----------
+
+ * Removed support for `service:action` syntax to reference controllers. Use `serviceOrFqcn::method` instead.
+
 Messenger
 ---------
 
diff --git a/src/Symfony/Bundle/WebProfilerBundle/Tests/Controller/ProfilerControllerTest.php b/src/Symfony/Bundle/WebProfilerBundle/Tests/Controller/ProfilerControllerTest.php
index d5479ecefc168..d9ece4216d5b8 100644
--- a/src/Symfony/Bundle/WebProfilerBundle/Tests/Controller/ProfilerControllerTest.php
+++ b/src/Symfony/Bundle/WebProfilerBundle/Tests/Controller/ProfilerControllerTest.php
@@ -71,7 +71,7 @@ public function testPanelActionWithLatestToken()
         $client->request('GET', '/');
         $client->request('GET', '/_profiler/latest');
 
-        $this->assertStringContainsString('kernel:homepageController', $client->getResponse()->getContent());
+        $this->assertStringContainsString('kernel::homepageController', $client->getResponse()->getContent());
     }
 
     public function testPanelActionWithoutValidToken()
diff --git a/src/Symfony/Bundle/WebProfilerBundle/Tests/Functional/WebProfilerBundleKernel.php b/src/Symfony/Bundle/WebProfilerBundle/Tests/Functional/WebProfilerBundleKernel.php
index 76c224d0777fe..df3054bdea06d 100644
--- a/src/Symfony/Bundle/WebProfilerBundle/Tests/Functional/WebProfilerBundleKernel.php
+++ b/src/Symfony/Bundle/WebProfilerBundle/Tests/Functional/WebProfilerBundleKernel.php
@@ -34,7 +34,7 @@ protected function configureRoutes(RoutingConfigurator $routes)
     {
         $routes->import(__DIR__.'/../../Resources/config/routing/profiler.xml')->prefix('/_profiler');
         $routes->import(__DIR__.'/../../Resources/config/routing/wdt.xml')->prefix('/_wdt');
-        $routes->add('_', '/')->controller('kernel:homepageController');
+        $routes->add('_', '/')->controller('kernel::homepageController');
     }
 
     protected function configureContainer(ContainerBuilder $containerBuilder, LoaderInterface $loader)
diff --git a/src/Symfony/Component/HttpKernel/CHANGELOG.md b/src/Symfony/Component/HttpKernel/CHANGELOG.md
index ada9fafe60102..fbffdce68c5a7 100644
--- a/src/Symfony/Component/HttpKernel/CHANGELOG.md
+++ b/src/Symfony/Component/HttpKernel/CHANGELOG.md
@@ -4,6 +4,7 @@ CHANGELOG
 5.1.0
 -----
 
+ * deprecated support for `service:action` syntax to reference controllers, use `serviceOrFqcn::method` instead
  * allowed using public aliases to reference controllers
  * added session usage reporting when the `_stateless` attribute of the request is set to `true`
 
@@ -11,8 +12,8 @@ CHANGELOG
 -----
 
  * removed support for getting the container from a non-booted kernel
- * removed the first and second constructor argument of `ConfigDataCollector` 
- * removed `ConfigDataCollector::getApplicationName()` 
+ * removed the first and second constructor argument of `ConfigDataCollector`
+ * removed `ConfigDataCollector::getApplicationName()`
  * removed `ConfigDataCollector::getApplicationVersion()`
  * removed support for `Symfony\Component\Templating\EngineInterface` in `HIncludeFragmentRenderer`, use a `Twig\Environment` only
  * removed `TranslatorListener` in favor of `LocaleAwareListener`
@@ -24,7 +25,7 @@ CHANGELOG
  * removed `GetResponseForControllerResultEvent`, use `ViewEvent` instead
  * removed `GetResponseForExceptionEvent`, use `ExceptionEvent` instead
  * removed `PostResponseEvent`, use `TerminateEvent` instead
- * removed `SaveSessionListener` in favor of `AbstractSessionListener` 
+ * removed `SaveSessionListener` in favor of `AbstractSessionListener`
  * removed `Client`, use `HttpKernelBrowser` instead
  * added method `getProjectDir()` to `KernelInterface`
  * removed methods `serialize` and `unserialize` from `DataCollector`, store the serialized state in the data property instead
diff --git a/src/Symfony/Component/HttpKernel/Controller/ContainerControllerResolver.php b/src/Symfony/Component/HttpKernel/Controller/ContainerControllerResolver.php
index 6e4ae20c34ce8..3b9468465c52c 100644
--- a/src/Symfony/Component/HttpKernel/Controller/ContainerControllerResolver.php
+++ b/src/Symfony/Component/HttpKernel/Controller/ContainerControllerResolver.php
@@ -16,7 +16,7 @@
 use Symfony\Component\DependencyInjection\Container;
 
 /**
- * A controller resolver searching for a controller in a psr-11 container when using the "service:method" notation.
+ * A controller resolver searching for a controller in a psr-11 container when using the "service::method" notation.
  *
  * @author Fabien Potencier <fabien@symfony.com>
  * @author Maxime Steinhausser <maxime.steinhausser@gmail.com>
@@ -36,7 +36,7 @@ protected function createController(string $controller)
     {
         if (1 === substr_count($controller, ':')) {
             $controller = str_replace(':', '::', $controller);
-            // TODO deprecate this in 5.1
+            trigger_deprecation('symfony/http-kernel', '5.1', 'Referencing controllers with a single colon is deprecated. Use "%s" instead.', $controller);
         }
 
         return parent::createController($controller);
diff --git a/src/Symfony/Component/HttpKernel/Tests/Controller/ContainerControllerResolverTest.php b/src/Symfony/Component/HttpKernel/Tests/Controller/ContainerControllerResolverTest.php
index c39dac3ca59d8..85dd5fb67175d 100644
--- a/src/Symfony/Component/HttpKernel/Tests/Controller/ContainerControllerResolverTest.php
+++ b/src/Symfony/Component/HttpKernel/Tests/Controller/ContainerControllerResolverTest.php
@@ -19,6 +19,10 @@
 
 class ContainerControllerResolverTest extends ControllerResolverTest
 {
+    /**
+     * @group legacy
+     * @expectedDeprecation Since symfony/http-kernel 5.1: Referencing controllers with a single colon is deprecated. Use "foo::action" instead.
+     */
     public function testGetControllerServiceWithSingleColon()
     {
         $service = new ControllerTestService('foo');
@@ -145,7 +149,6 @@ public function getControllers()
     {
         return [
             ['\\'.ControllerTestService::class.'::action'],
-            ['\\'.ControllerTestService::class.':action'],
         ];
     }
 
diff --git a/src/Symfony/Component/HttpKernel/composer.json b/src/Symfony/Component/HttpKernel/composer.json
index e60792f689190..ec5ea1277cd24 100644
--- a/src/Symfony/Component/HttpKernel/composer.json
+++ b/src/Symfony/Component/HttpKernel/composer.json
@@ -17,6 +17,7 @@
     ],
     "require": {
         "php": "^7.2.5",
+        "symfony/deprecation-contracts": "^2.1",
         "symfony/error-handler": "^4.4|^5.0",
         "symfony/event-dispatcher": "^5.0",
         "symfony/http-foundation": "^4.4|^5.0",