diff --git a/core/lib/Drupal/Component/HttpFoundation/SecuredRedirectResponse.php b/core/lib/Drupal/Component/HttpFoundation/SecuredRedirectResponse.php
index 58a5a57d79..931f816062 100644
--- a/core/lib/Drupal/Component/HttpFoundation/SecuredRedirectResponse.php
+++ b/core/lib/Drupal/Component/HttpFoundation/SecuredRedirectResponse.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\Component\HttpFoundation;
 
-use \Symfony\Component\HttpFoundation\RedirectResponse;
+use Symfony\Component\HttpFoundation\RedirectResponse;
 
 /**
  * Provides a common base class for safe redirects.
diff --git a/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php b/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php
index 37d9078a05..90ee661201 100644
--- a/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php
+++ b/core/lib/Drupal/Component/Plugin/ContextAwarePluginInterface.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\Component\Plugin;
 
-use \Drupal\Component\Plugin\Context\ContextInterface;
+use Drupal\Component\Plugin\Context\ContextInterface;
 
 /**
  * Interface for defining context aware plugins.
diff --git a/core/lib/Drupal/Component/Plugin/Exception/InvalidDecoratedMethod.php b/core/lib/Drupal/Component/Plugin/Exception/InvalidDecoratedMethod.php
index bf2b335fd3..0244e03394 100644
--- a/core/lib/Drupal/Component/Plugin/Exception/InvalidDecoratedMethod.php
+++ b/core/lib/Drupal/Component/Plugin/Exception/InvalidDecoratedMethod.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\Component\Plugin\Exception;
 
-use \BadMethodCallException;
+use BadMethodCallException;
 
 /**
  * Exception thrown when a decorator's _call() method is triggered, but the
diff --git a/core/lib/Drupal/Core/Config/ConfigBase.php b/core/lib/Drupal/Core/Config/ConfigBase.php
index 596ed92156..4f445ea21c 100644
--- a/core/lib/Drupal/Core/Config/ConfigBase.php
+++ b/core/lib/Drupal/Core/Config/ConfigBase.php
@@ -7,7 +7,7 @@
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Cache\RefinableCacheableDependencyInterface;
 use Drupal\Core\Cache\RefinableCacheableDependencyTrait;
-use \Drupal\Core\DependencyInjection\DependencySerializationTrait;
+use Drupal\Core\DependencyInjection\DependencySerializationTrait;
 
 /**
  * Provides a base class for configuration objects with get/set support.
diff --git a/core/lib/Drupal/Core/Routing/RouteProvider.php b/core/lib/Drupal/Core/Routing/RouteProvider.php
index 5d92e77e0f..2417358a1d 100644
--- a/core/lib/Drupal/Core/Routing/RouteProvider.php
+++ b/core/lib/Drupal/Core/Routing/RouteProvider.php
@@ -15,7 +15,7 @@
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\Routing\Exception\RouteNotFoundException;
 use Symfony\Component\Routing\RouteCollection;
-use \Drupal\Core\Database\Connection;
+use Drupal\Core\Database\Connection;
 
 /**
  * A Route Provider front-end for all Drupal-stored routes.
diff --git a/core/lib/Drupal/Core/StreamWrapper/TemporaryStream.php b/core/lib/Drupal/Core/StreamWrapper/TemporaryStream.php
index 830fb93c47..5e1e56b9f5 100644
--- a/core/lib/Drupal/Core/StreamWrapper/TemporaryStream.php
+++ b/core/lib/Drupal/Core/StreamWrapper/TemporaryStream.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\Core\StreamWrapper;
 
-use \Drupal\Core\Url;
+use Drupal\Core\Url;
 
 /**
  * Defines a Drupal temporary (temporary://) stream wrapper class.
diff --git a/core/modules/content_translation/content_translation.install b/core/modules/content_translation/content_translation.install
index 67b161c5e2..455d5ed3d8 100644
--- a/core/modules/content_translation/content_translation.install
+++ b/core/modules/content_translation/content_translation.install
@@ -5,9 +5,9 @@
  * Installation functions for Content Translation module.
  */
 
-use \Drupal\Core\Entity\Sql\SqlEntityStorageInterface;
-use \Drupal\Core\Language\LanguageInterface;
-use \Drupal\Core\Url;
+use Drupal\Core\Entity\Sql\SqlEntityStorageInterface;
+use Drupal\Core\Language\LanguageInterface;
+use Drupal\Core\Url;
 
 /**
  * Implements hook_install().
diff --git a/core/modules/content_translation/tests/modules/content_translation_test/content_translation_test.module b/core/modules/content_translation/tests/modules/content_translation_test/content_translation_test.module
index d07549da0b..e2318079c9 100644
--- a/core/modules/content_translation/tests/modules/content_translation_test/content_translation_test.module
+++ b/core/modules/content_translation/tests/modules/content_translation_test/content_translation_test.module
@@ -5,7 +5,7 @@
  * Helper module for the Content Translation tests.
  */
 
-use \Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Form\FormStateInterface;
 
 /**
  * Implements hook_form_BASE_FORM_ID_alter().
diff --git a/core/modules/help/tests/modules/help_page_test/help_page_test.module b/core/modules/help/tests/modules/help_page_test/help_page_test.module
index 67bcac33a8..f57728d53f 100644
--- a/core/modules/help/tests/modules/help_page_test/help_page_test.module
+++ b/core/modules/help/tests/modules/help_page_test/help_page_test.module
@@ -5,7 +5,7 @@
  * Help Page Test module to test the help page.
  */
 
-use \Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
 
 /**
  * Implements hook_help().
diff --git a/core/modules/help/tests/modules/help_test/help_test.module b/core/modules/help/tests/modules/help_test/help_test.module
index 2fd49912ed..9f67eccc65 100644
--- a/core/modules/help/tests/modules/help_test/help_test.module
+++ b/core/modules/help/tests/modules/help_test/help_test.module
@@ -5,7 +5,7 @@
  * Test Help module.
  */
 
-use \Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
 
 /**
  * Implements hook_help().
diff --git a/core/modules/help/tests/modules/more_help_page_test/more_help_page_test.module b/core/modules/help/tests/modules/more_help_page_test/more_help_page_test.module
index 60eb4fc830..4bc939751c 100644
--- a/core/modules/help/tests/modules/more_help_page_test/more_help_page_test.module
+++ b/core/modules/help/tests/modules/more_help_page_test/more_help_page_test.module
@@ -5,7 +5,7 @@
  * More Help Page Test module to test the help blocks.
  */
 
-use \Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
 
 /**
  * Implements hook_help().
diff --git a/core/modules/media/media.install b/core/modules/media/media.install
index 7698b18ebf..3ff51594b9 100644
--- a/core/modules/media/media.install
+++ b/core/modules/media/media.install
@@ -5,7 +5,7 @@
  * Install, uninstall and update hooks for Media module.
  */
 
-use \Drupal\user\RoleInterface;
+use Drupal\user\RoleInterface;
 
 /**
  * Implements hook_install().
diff --git a/core/modules/menu_link_content/src/Plugin/migrate/process/d6/LinkUri.php b/core/modules/menu_link_content/src/Plugin/migrate/process/d6/LinkUri.php
index 0a4c918387..7467c72f19 100644
--- a/core/modules/menu_link_content/src/Plugin/migrate/process/d6/LinkUri.php
+++ b/core/modules/menu_link_content/src/Plugin/migrate/process/d6/LinkUri.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\menu_link_content\Plugin\migrate\process\d6;
 
-use \Drupal\menu_link_content\Plugin\migrate\process\LinkUri as RealLinkUri;
+use Drupal\menu_link_content\Plugin\migrate\process\LinkUri as RealLinkUri;
 
 /**
  * Processes a link path into an 'internal:' or 'entity:' URI.
diff --git a/core/modules/rest/src/Annotation/RestResource.php b/core/modules/rest/src/Annotation/RestResource.php
index d21f24c5f0..f525ff1c84 100644
--- a/core/modules/rest/src/Annotation/RestResource.php
+++ b/core/modules/rest/src/Annotation/RestResource.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\rest\Annotation;
 
-use \Drupal\Component\Annotation\Plugin;
+use Drupal\Component\Annotation\Plugin;
 
 /**
  * Defines a REST resource annotation object.
diff --git a/core/modules/system/tests/modules/common_test/common_test.module b/core/modules/system/tests/modules/common_test/common_test.module
index 97bba7b341..040e40a4e4 100644
--- a/core/modules/system/tests/modules/common_test/common_test.module
+++ b/core/modules/system/tests/modules/common_test/common_test.module
@@ -5,7 +5,7 @@
  * Helper module for the Common tests.
  */
 
-use \Drupal\Core\Asset\AttachedAssetsInterface;
+use Drupal\Core\Asset\AttachedAssetsInterface;
 
 /**
  * Applies #printed to an element to help test #pre_render.
diff --git a/core/modules/system/tests/modules/entity_test_schema_converter/entity_test_schema_converter.post_update.php b/core/modules/system/tests/modules/entity_test_schema_converter/entity_test_schema_converter.post_update.php
index 1de5790071..ecddf31058 100644
--- a/core/modules/system/tests/modules/entity_test_schema_converter/entity_test_schema_converter.post_update.php
+++ b/core/modules/system/tests/modules/entity_test_schema_converter/entity_test_schema_converter.post_update.php
@@ -5,7 +5,7 @@
  * Post update functions for entity_test_schema_converter.
  */
 
-use \Drupal\Core\Entity\Sql\SqlContentEntityStorageSchemaConverter;
+use Drupal\Core\Entity\Sql\SqlContentEntityStorageSchemaConverter;
 
 /**
  * @addtogroup updates-8.4.x
diff --git a/core/modules/system/tests/modules/experimental_module_test/experimental_module_test.module b/core/modules/system/tests/modules/experimental_module_test/experimental_module_test.module
index ec3ae7f207..1f5072085f 100644
--- a/core/modules/system/tests/modules/experimental_module_test/experimental_module_test.module
+++ b/core/modules/system/tests/modules/experimental_module_test/experimental_module_test.module
@@ -5,7 +5,7 @@
  * Experimental Test module to test the Core (Experimental) package.
  */
 
-use \Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
 
 /**
  * Implements hook_help().
diff --git a/core/modules/system/tests/src/Kernel/Extension/ModuleHandlerTest.php b/core/modules/system/tests/src/Kernel/Extension/ModuleHandlerTest.php
index 5fc9d83732..d7c2650353 100644
--- a/core/modules/system/tests/src/Kernel/Extension/ModuleHandlerTest.php
+++ b/core/modules/system/tests/src/Kernel/Extension/ModuleHandlerTest.php
@@ -3,7 +3,7 @@
 namespace Drupal\Tests\system\Kernel\Extension;
 
 use Drupal\Core\Extension\MissingDependencyException;
-use \Drupal\Core\Extension\ModuleUninstallValidatorException;
+use Drupal\Core\Extension\ModuleUninstallValidatorException;
 use Drupal\entity_test\Entity\EntityTest;
 use Drupal\KernelTests\KernelTestBase;
 
diff --git a/core/modules/taxonomy/tests/src/Functional/LegacyTest.php b/core/modules/taxonomy/tests/src/Functional/LegacyTest.php
index ac8e82dd66..667ed5542f 100644
--- a/core/modules/taxonomy/tests/src/Functional/LegacyTest.php
+++ b/core/modules/taxonomy/tests/src/Functional/LegacyTest.php
@@ -4,7 +4,7 @@
 
 use Drupal\Core\Datetime\DrupalDateTime;
 use Drupal\Core\Field\FieldStorageDefinitionInterface;
-use \Drupal\taxonomy\Entity\Vocabulary;
+use Drupal\taxonomy\Entity\Vocabulary;
 
 /**
  * Posts an article with a taxonomy term and a date prior to 1970.
diff --git a/core/phpcs.xml.dist b/core/phpcs.xml.dist
index a593e62c7d..e2c59d6cab 100644
--- a/core/phpcs.xml.dist
+++ b/core/phpcs.xml.dist
@@ -16,6 +16,7 @@
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/Classes/ClassDeclarationSniff.php"/>
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/Classes/FullyQualifiedNamespaceSniff.php"/>
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/Classes/UnusedUseStatementSniff.php"/>
+  <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/Classes/UseLeadingBackslashSniff.php"/>
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/CSS/ClassDefinitionNameSpacingSniff.php"/>
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/CSS/ColourDefinitionSniff.php"/>
   <rule ref="../vendor/drupal/coder/coder_sniffer/Drupal/Sniffs/Commenting/ClassCommentSniff.php">
diff --git a/core/tests/Drupal/Tests/Component/Utility/CryptRandomFallbackTest.php b/core/tests/Drupal/Tests/Component/Utility/CryptRandomFallbackTest.php
index 52d91de33f..c87af872b3 100644
--- a/core/tests/Drupal/Tests/Component/Utility/CryptRandomFallbackTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/CryptRandomFallbackTest.php
@@ -52,7 +52,7 @@ public function testRandomBytesFallback() {
 
 namespace Drupal\Component\Utility;
 
-use  \Drupal\Tests\Component\Utility\CryptRandomFallbackTest;
+use  Drupal\Tests\Component\Utility\CryptRandomFallbackTest;
 
 /**
  * Defines a function in same namespace as Drupal\Component\Utility\Crypt.
diff --git a/core/tests/Drupal/Tests/Core/EventSubscriber/PsrResponseSubscriberTest.php b/core/tests/Drupal/Tests/Core/EventSubscriber/PsrResponseSubscriberTest.php
index 38ae7f7d77..c18b109ee7 100644
--- a/core/tests/Drupal/Tests/Core/EventSubscriber/PsrResponseSubscriberTest.php
+++ b/core/tests/Drupal/Tests/Core/EventSubscriber/PsrResponseSubscriberTest.php
@@ -3,7 +3,7 @@
 namespace Drupal\Tests\Core\EventSubscriber;
 
 use Drupal\Tests\UnitTestCase;
-use \Drupal\Core\EventSubscriber\PsrResponseSubscriber;
+use Drupal\Core\EventSubscriber\PsrResponseSubscriber;
 
 /**
  * @coversDefaultClass \Drupal\Core\EventSubscriber\PsrResponseSubscriber
diff --git a/core/tests/Drupal/Tests/Traits/Core/Config/SchemaConfigListenerTestTrait.php b/core/tests/Drupal/Tests/Traits/Core/Config/SchemaConfigListenerTestTrait.php
index e2cc00cf4d..5a73cad4bb 100644
--- a/core/tests/Drupal/Tests/Traits/Core/Config/SchemaConfigListenerTestTrait.php
+++ b/core/tests/Drupal/Tests/Traits/Core/Config/SchemaConfigListenerTestTrait.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\Tests\Traits\Core\Config;
 
-use \Drupal\Core\Config\Schema\SchemaIncompleteException;
+use Drupal\Core\Config\Schema\SchemaIncompleteException;
 
 /**
  * Adds a test for the configuration schema checker use in tests.
