diff --git a/src/Framework/TestRunner/IsolatedTestRunnerRegistry.php b/src/Framework/TestRunner/IsolatedTestRunnerRegistry.php
index 058246543a..e6c8f85f40 100644
--- a/src/Framework/TestRunner/IsolatedTestRunnerRegistry.php
+++ b/src/Framework/TestRunner/IsolatedTestRunnerRegistry.php
@@ -9,6 +9,10 @@
  */
 namespace PHPUnit\Framework;
 
+use PHPUnit\Event\Facade;
+use PHPUnit\Runner\CodeCoverage;
+use PHPUnit\TestRunner\TestResult\PassedTests;
+
 /**
  * @no-named-arguments Parameter names are not covered by the backward compatibility promise for PHPUnit
  *
@@ -16,7 +20,8 @@
  */
 final class IsolatedTestRunnerRegistry
 {
-    private static ?IsolatedTestRunner $runner = null;
+    private static ?IsolatedTestRunner $runner             = null;
+    private static ?PcntlForkJobRunner $pcntlForkJobRunner = null;
 
     public static function run(TestCase $test, bool $runEntireClass, bool $preserveGlobalState): void
     {
@@ -24,6 +29,14 @@ public static function run(TestCase $test, bool $runEntireClass, bool $preserveG
             self::$runner = new SeparateProcessTestRunner;
         }
 
+        $pcntlForkJobRunner = self::pcntlForkRunner();
+
+        if ($pcntlForkJobRunner->canRun($test, $runEntireClass, $preserveGlobalState)) {
+            $pcntlForkJobRunner->run($test, $runEntireClass, $preserveGlobalState);
+
+            return;
+        }
+
         self::$runner->run($test, $runEntireClass, $preserveGlobalState);
     }
 
@@ -31,4 +44,20 @@ public static function set(IsolatedTestRunner $runner): void
     {
         self::$runner = $runner;
     }
+
+    private static function pcntlForkRunner(): PcntlForkJobRunner
+    {
+        if (self::$pcntlForkJobRunner === null) {
+            self::$pcntlForkJobRunner = new PcntlForkJobRunner(
+                new ChildProcessResultProcessor(
+                    Facade::instance(),
+                    Facade::emitter(),
+                    PassedTests::instance(),
+                    CodeCoverage::instance(),
+                ),
+            );
+        }
+
+        return self::$pcntlForkJobRunner;
+    }
 }
diff --git a/src/Framework/TestRunner/PcntlForkJobRunner.php b/src/Framework/TestRunner/PcntlForkJobRunner.php
new file mode 100644
index 0000000000..5198db9620
--- /dev/null
+++ b/src/Framework/TestRunner/PcntlForkJobRunner.php
@@ -0,0 +1,126 @@
+<?php declare(strict_types=1);
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+namespace PHPUnit\Framework;
+
+use function file_get_contents;
+use function file_put_contents;
+use function function_exists;
+use function get_included_files;
+use function hrtime;
+use function in_array;
+use function ini_get;
+use function pcntl_fork;
+use function pcntl_waitpid;
+use function serialize;
+use function str_contains;
+use function sys_get_temp_dir;
+use function tempnam;
+use Exception;
+use PHPUnit\Event\Facade;
+use PHPUnit\Event\Facade as EventFacade;
+use PHPUnit\Event\Telemetry\HRTime;
+use PHPUnit\Runner\CodeCoverage;
+use PHPUnit\TestRunner\TestResult\PassedTests;
+use PHPUnit\TextUI\Configuration\Registry as ConfigurationRegistry;
+
+/**
+ * @no-named-arguments Parameter names are not covered by the backward compatibility promise for PHPUnit
+ *
+ * @internal This class is not covered by the backward compatibility promise for PHPUnit
+ */
+final class PcntlForkJobRunner implements IsolatedTestRunner
+{
+    public function __construct(private ChildProcessResultProcessor $processor)
+    {
+    }
+
+    public function run(TestCase $test, bool $runEntireClass, bool $preserveGlobalState): void
+    {
+        $processResultFile = tempnam(sys_get_temp_dir(), 'phpunit_');
+
+        $pid = pcntl_fork();
+
+        if ($pid === -1) {
+            // @codeCoverageIgnoreStart
+            throw new Exception('could not fork');
+            // @codeCoverageIgnoreEnd
+        }
+
+        if ($pid !== 0) {
+            // we are the parent
+            Facade::emitter()->childProcessStarted();
+
+            pcntl_waitpid($pid, $status);
+
+            $this->processor->process($test, file_get_contents($processResultFile), '');
+
+            EventFacade::emitter()->childProcessFinished('', '');
+
+            return;
+        }
+
+        // we are the child, run the test
+
+        $offset     = hrtime();
+        $dispatcher = Facade::instance()->initForIsolation(
+            HRTime::fromSecondsAndNanoseconds(
+                $offset[0],
+                $offset[1],
+            ),
+        );
+
+        $test->setInIsolation(true);
+        $test->run();
+
+        file_put_contents(
+            $processResultFile,
+            serialize(
+                (object) [
+                    'testResult'    => $test->result(),
+                    'codeCoverage'  => CodeCoverage::instance()->isActive() ? CodeCoverage::instance()->codeCoverage() : null,
+                    'numAssertions' => $test->numberOfAssertionsPerformed(),
+                    'output'        => !$test->expectsOutput() ? $test->output() : '',
+                    'events'        => $dispatcher->flush(),
+                    'passedTests'   => PassedTests::instance(),
+                ],
+            ),
+        );
+
+        exit();
+    }
+
+    public function canRun(TestCase $test, bool $runEntireClass, bool $preserveGlobalState): bool
+    {
+        if (!$this->isPcntlForkAvailable()) {
+            return false;
+        }
+
+        // we support bootstrap files only if they have been already included in the parent process
+        // as we cannot require a file and load it into the global scope from within a forked process.
+        if (ConfigurationRegistry::get()->hasBootstrap()) {
+            if (!in_array(ConfigurationRegistry::get()->bootstrap(), get_included_files(), true)) {
+                return false;
+            }
+        }
+
+        return !$runEntireClass &&
+            !$preserveGlobalState;
+    }
+
+    private function isPcntlForkAvailable(): bool
+    {
+        $disabledFunctions = ini_get('disable_functions');
+
+        return
+            function_exists('pcntl_fork') &&
+            function_exists('pcntl_waitpid') &&
+            !str_contains($disabledFunctions, 'pcntl');
+    }
+}