diff --git a/django/test/runner.py b/django/test/runner.py
index fb4d77ed60..4232e82e9b 100644
--- a/django/test/runner.py
+++ b/django/test/runner.py
@@ -11,7 +11,6 @@ import random
 import sys
 import textwrap
 import unittest
-import warnings
 from collections import defaultdict
 from contextlib import contextmanager
 from importlib import import_module
@@ -30,7 +29,6 @@ from django.test.utils import teardown_databases as _teardown_databases
 from django.test.utils import teardown_test_environment
 from django.utils.crypto import new_hash
 from django.utils.datastructures import OrderedSet
-from django.utils.deprecation import RemovedInDjango50Warning
 
 try:
     import ipdb as pdb
@@ -877,15 +875,8 @@ class DiscoverRunner:
         self.test_loader._top_level_dir = None
         return tests
 
-    def build_suite(self, test_labels=None, extra_tests=None, **kwargs):
-        if extra_tests is not None:
-            warnings.warn(
-                "The extra_tests argument is deprecated.",
-                RemovedInDjango50Warning,
-                stacklevel=2,
-            )
+    def build_suite(self, test_labels=None, **kwargs):
         test_labels = test_labels or ["."]
-        extra_tests = extra_tests or []
 
         discover_kwargs = {}
         if self.pattern is not None:
@@ -899,8 +890,6 @@ class DiscoverRunner:
             tests = self.load_tests_for_label(label, discover_kwargs)
             all_tests.extend(iter_test_cases(tests))
 
-        all_tests.extend(iter_test_cases(extra_tests))
-
         if self.tags or self.exclude_tags:
             if self.tags:
                 self.log(
@@ -1030,7 +1019,7 @@ class DiscoverRunner:
             )
         return databases
 
-    def run_tests(self, test_labels, extra_tests=None, **kwargs):
+    def run_tests(self, test_labels, **kwargs):
         """
         Run the unit tests for all the test labels in the provided list.
 
@@ -1039,14 +1028,8 @@ class DiscoverRunner:
 
         Return the number of tests that failed.
         """
-        if extra_tests is not None:
-            warnings.warn(
-                "The extra_tests argument is deprecated.",
-                RemovedInDjango50Warning,
-                stacklevel=2,
-            )
         self.setup_test_environment()
-        suite = self.build_suite(test_labels, extra_tests)
+        suite = self.build_suite(test_labels)
         databases = self.get_databases(suite)
         suite.serialized_aliases = set(
             alias for alias, serialize in databases.items() if serialize
diff --git a/docs/releases/5.0.txt b/docs/releases/5.0.txt
index f2904d3359..12478e0b89 100644
--- a/docs/releases/5.0.txt
+++ b/docs/releases/5.0.txt
@@ -267,6 +267,9 @@ to remove usage of these features.
 * The default sitemap protocol for sitemaps built outside the context of a
   request is changed from ``'http'`` to ``'https'``.
 
+* The ``extra_tests`` argument for ``DiscoverRunner.build_suite()`` and
+  ``DiscoverRunner.run_tests()`` is removed.
+
 See :ref:`deprecated-features-4.1` for details on these changes, including how
 to remove usage of these features.
 
diff --git a/docs/topics/testing/advanced.txt b/docs/topics/testing/advanced.txt
index 4afb36db3d..07fb881aee 100644
--- a/docs/topics/testing/advanced.txt
+++ b/docs/topics/testing/advanced.txt
@@ -654,12 +654,6 @@ Methods
     several formats (see :meth:`DiscoverRunner.build_suite` for a list of
     supported formats).
 
-    .. deprecated:: 4.0
-
-        ``extra_tests`` is a list of extra ``TestCase`` instances to add to the
-        suite that is executed by the test runner. These extra tests are run in
-        addition to those discovered in the modules listed in ``test_labels``.
-
     This method should return the number of tests that failed.
 
 .. classmethod:: DiscoverRunner.add_arguments(parser)
@@ -695,12 +689,6 @@ Methods
     tests in all files below the current directory whose names match its
     ``pattern`` (see above).
 
-    .. deprecated:: 4.0
-
-        ``extra_tests`` is a list of extra ``TestCase`` instances to add to the
-        suite that is executed by the test runner. These extra tests are run in
-        addition to those discovered in the modules listed in ``test_labels``.
-
     Returns a ``TestSuite`` instance ready to be run.
 
 .. method:: DiscoverRunner.setup_databases(**kwargs)
diff --git a/tests/test_runner/tests.py b/tests/test_runner/tests.py
index 8f39b73e9f..fca430e93f 100644
--- a/tests/test_runner/tests.py
+++ b/tests/test_runner/tests.py
@@ -31,7 +31,6 @@ from django.test.utils import (
     get_unique_databases_and_mirrors,
     iter_test_cases,
 )
-from django.utils.deprecation import RemovedInDjango50Warning
 
 from .models import B, Person, Through
 
@@ -1033,42 +1032,3 @@ class RunTestsExceptionHandlingTests(unittest.TestCase):
                     )
             self.assertTrue(teardown_databases.called)
             self.assertFalse(teardown_test_environment.called)
-
-
-# RemovedInDjango50Warning
-class NoOpTestRunner(DiscoverRunner):
-    def setup_test_environment(self, **kwargs):
-        return
-
-    def setup_databases(self, **kwargs):
-        return
-
-    def run_checks(self, databases):
-        return
-
-    def teardown_databases(self, old_config, **kwargs):
-        return
-
-    def teardown_test_environment(self, **kwargs):
-        return
-
-
-class DiscoverRunnerExtraTestsDeprecationTests(SimpleTestCase):
-    msg = "The extra_tests argument is deprecated."
-
-    def get_runner(self):
-        return NoOpTestRunner(verbosity=0, interactive=False)
-
-    def test_extra_tests_build_suite(self):
-        runner = self.get_runner()
-        with self.assertWarnsMessage(RemovedInDjango50Warning, self.msg):
-            runner.build_suite(extra_tests=[])
-
-    def test_extra_tests_run_tests(self):
-        runner = self.get_runner()
-        with captured_stderr():
-            with self.assertWarnsMessage(RemovedInDjango50Warning, self.msg):
-                runner.run_tests(
-                    test_labels=["test_runner_apps.sample.tests_sample.EmptyTestCase"],
-                    extra_tests=[],
-                )