diff --git a/phpstan.neon b/phpstan.neon
index fa25c0a2eb2..701ec1fe665 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -5,6 +5,7 @@ includes:
 rules:
     - Rector\Utils\PHPStan\Rule\RegisterRelatedPolyfillRectorRule
     - Rector\Utils\PHPStan\Rule\NoResolveClassReflectionInForeachRule
+    - Rector\Utils\PHPStan\Rule\RegisterRectorRule
 
 parameters:
     level: 8
@@ -228,6 +229,19 @@ parameters:
                 - rules/Php81/Rector/FuncCall/NullToStrictStringFuncCallArgRector.php
                 - rules/Php80/Rector/NotIdentical/MbStrContainsRector.php
 
+        # not registered in a rector-src set on purpose: NullToStrictString is opt-in only (risky),
+        # the rest are registered in third-party sets (rector-laravel, drupal-rector) that cannot be
+        # installed here due to the rector/rector replace
+        -
+            identifier: rector.registerRector
+            paths:
+                - rules/Php81/Rector/FuncCall/NullToStrictStringFuncCallArgRector.php
+                - rules/Removing/Rector/Class_/RemoveTraitUseRector.php
+                - rules/Renaming/Rector/StaticCall/RenameStaticMethodRector.php
+                - rules/Transform/Rector/FuncCall/FuncCallToNewRector.php
+                - rules/Transform/Rector/FuncCall/FuncCallToStaticCallRector.php
+                - rules/Transform/Rector/String_/StringToClassConstantRector.php
+
         # lack of generic array in nikic/php-parser
         -
             identifier: return.type
diff --git a/utils/phpstan/src/Rule/RegisterRectorRule.php b/utils/phpstan/src/Rule/RegisterRectorRule.php
new file mode 100644
index 00000000000..10a68e73582
--- /dev/null
+++ b/utils/phpstan/src/Rule/RegisterRectorRule.php
@@ -0,0 +1,152 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Utils\PHPStan\Rule;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Node\InClassNode;
+use PHPStan\Rules\IdentifierRuleError;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+use Rector\Configuration\Deprecation\Contract\DeprecatedInterface;
+use Rector\Contract\Rector\RectorInterface;
+use RecursiveDirectoryIterator;
+use RecursiveIteratorIterator;
+use SplFileInfo;
+
+/**
+ * Every Rector rule must be registered in a set or level config, otherwise it can
+ * never run and becomes dead code. Registrations in sibling extension packages
+ * (rector-doctrine, rector-symfony, ...) count too. Deprecated rules are skipped,
+ * as they are intentionally unregistered.
+ *
+ * @implements Rule<InClassNode>
+ * @see \Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule\RegisterRectorRuleTest
+ */
+final class RegisterRectorRule implements Rule
+{
+    private const string ERROR_MESSAGE = 'Rector rule "%s" is not registered in any set or level config, so it can never run. Register it in a set/level, or deprecate it if it is no longer wanted.';
+
+    /**
+     * @var string[]
+     */
+    private readonly array $registrationDirectories;
+
+    /**
+     * @var array<string, true>|null
+     */
+    private ?array $registeredShortClassNames = null;
+
+    /**
+     * @param string[]|null $registrationDirectories
+     */
+    public function __construct(?array $registrationDirectories = null)
+    {
+        $root = __DIR__ . '/../../../../';
+
+        $this->registrationDirectories = $registrationDirectories ?? array_merge(
+            [$root . 'config', $root . 'src/Config'],
+            // sibling extension packages register rules in their own config sets
+            glob($root . 'vendor/rector/*/config') ?: []
+        );
+    }
+
+    public function getNodeType(): string
+    {
+        return InClassNode::class;
+    }
+
+    /**
+     * @param InClassNode $node
+     * @return list<IdentifierRuleError>
+     */
+    public function processNode(Node $node, Scope $scope): array
+    {
+        $classReflection = $node->getClassReflection();
+
+        if ($classReflection->isAbstract()) {
+            return [];
+        }
+
+        if (! $classReflection->implementsInterface(RectorInterface::class)) {
+            return [];
+        }
+
+        // test doubles are wired directly in their test, not through a set
+        if (str_starts_with($classReflection->getName(), 'Rector\\Tests\\')) {
+            return [];
+        }
+
+        // intentionally unregistered
+        if ($classReflection->implementsInterface(DeprecatedInterface::class)) {
+            return [];
+        }
+
+        $className = $classReflection->getName();
+        if ($this->isRegistered($className)) {
+            return [];
+        }
+
+        return [
+            RuleErrorBuilder::message(sprintf(self::ERROR_MESSAGE, $className))
+                ->identifier('rector.registerRector')
+                ->build(),
+        ];
+    }
+
+    private function isRegistered(string $className): bool
+    {
+        $shortClassName = substr((string) strrchr($className, '\\'), 1);
+
+        // short class names are unique repo-wide (enforced by the "no duplicate short class names" check)
+        return isset($this->getRegisteredShortClassNames()[$shortClassName]);
+    }
+
+    /**
+     * Collect every "SomeRector::class" short name referenced in the scanned config directories once.
+     * The capture group stops at the preceding "\", so both "SomeRector::class" and a fully qualified
+     * "\Some\Ns\SomeRector::class" yield the same short name.
+     *
+     * @return array<string, true>
+     */
+    private function getRegisteredShortClassNames(): array
+    {
+        if ($this->registeredShortClassNames !== null) {
+            return $this->registeredShortClassNames;
+        }
+
+        $registeredShortClassNames = [];
+        foreach ($this->registrationDirectories as $registrationDirectory) {
+            if (! is_dir($registrationDirectory)) {
+                continue;
+            }
+
+            $recursiveIterator = new RecursiveIteratorIterator(
+                new RecursiveDirectoryIterator($registrationDirectory, RecursiveDirectoryIterator::SKIP_DOTS)
+            );
+
+            /** @var SplFileInfo $fileInfo */
+            foreach ($recursiveIterator as $fileInfo) {
+                if ($fileInfo->getExtension() !== 'php') {
+                    continue;
+                }
+
+                $fileContents = file_get_contents($fileInfo->getRealPath());
+                if ($fileContents === false) {
+                    continue;
+                }
+
+                preg_match_all('#([A-Za-z_][A-Za-z0-9_]*)::class#', $fileContents, $matches);
+                foreach ($matches[1] as $shortClassName) {
+                    $registeredShortClassNames[$shortClassName] = true;
+                }
+            }
+        }
+
+        $this->registeredShortClassNames = $registeredShortClassNames;
+
+        return $registeredShortClassNames;
+    }
+}
diff --git a/utils/phpstan/tests/Rule/RegisterRectorRule/RegisterRectorRuleTest.php b/utils/phpstan/tests/Rule/RegisterRectorRule/RegisterRectorRuleTest.php
new file mode 100644
index 00000000000..e3658c42b79
--- /dev/null
+++ b/utils/phpstan/tests/Rule/RegisterRectorRule/RegisterRectorRuleTest.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+use Rector\Utils\PHPStan\Rule\RegisterRectorRule;
+
+/**
+ * @extends RuleTestCase<RegisterRectorRule>
+ */
+final class RegisterRectorRuleTest extends RuleTestCase
+{
+    public function testUnregistered(): void
+    {
+        $expectedErrorMessage = 'Rector rule "Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule\Source\UnregisteredRector" is not registered in any set or level config, so it can never run. Register it in a set/level, or deprecate it if it is no longer wanted.';
+
+        $this->analyse([__DIR__ . '/Source/UnregisteredRector.php'], [[$expectedErrorMessage, 12]]);
+    }
+
+    public function testUnregisteredConfigurable(): void
+    {
+        $expectedErrorMessage = 'Rector rule "Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule\Source\UnregisteredConfigurableRector" is not registered in any set or level config, so it can never run. Register it in a set/level, or deprecate it if it is no longer wanted.';
+
+        $this->analyse([__DIR__ . '/Source/UnregisteredConfigurableRector.php'], [[$expectedErrorMessage, 13]]);
+    }
+
+    public function testRegistered(): void
+    {
+        $this->analyse([__DIR__ . '/Source/RegisteredRector.php'], []);
+    }
+
+    public function testRegisteredInSiblingConfig(): void
+    {
+        $this->analyse([__DIR__ . '/Source/SiblingRegisteredRector.php'], []);
+    }
+
+    public function testSkipDeprecated(): void
+    {
+        $this->analyse([__DIR__ . '/Source/SkipDeprecatedRector.php'], []);
+    }
+
+    protected function getRule(): Rule
+    {
+        return new RegisterRectorRule([__DIR__ . '/config', __DIR__ . '/config-sibling']);
+    }
+}
diff --git a/utils/phpstan/tests/Rule/RegisterRectorRule/Source/RegisteredRector.php b/utils/phpstan/tests/Rule/RegisterRectorRule/Source/RegisteredRector.php
new file mode 100644
index 00000000000..f34c1e6e5f6
--- /dev/null
+++ b/utils/phpstan/tests/Rule/RegisterRectorRule/Source/RegisteredRector.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule\Source;
+
+use PhpParser\Node;
+use Rector\Rector\AbstractRector;
+use Rector\RuleDoc\CodeSample\CodeSample;
+use Rector\RuleDoc\RuleDefinition;
+
+final class RegisteredRector extends AbstractRector
+{
+    public function getRuleDefinition(): RuleDefinition
+    {
+        return new RuleDefinition('Registered rule', [new CodeSample('before', 'after')]);
+    }
+
+    public function getNodeTypes(): array
+    {
+        return [Node::class];
+    }
+
+    public function refactor(Node $node): ?Node
+    {
+        return null;
+    }
+}
diff --git a/utils/phpstan/tests/Rule/RegisterRectorRule/Source/SiblingRegisteredRector.php b/utils/phpstan/tests/Rule/RegisterRectorRule/Source/SiblingRegisteredRector.php
new file mode 100644
index 00000000000..40660ee7d25
--- /dev/null
+++ b/utils/phpstan/tests/Rule/RegisterRectorRule/Source/SiblingRegisteredRector.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule\Source;
+
+use PhpParser\Node;
+use Rector\Rector\AbstractRector;
+use Rector\RuleDoc\CodeSample\CodeSample;
+use Rector\RuleDoc\RuleDefinition;
+
+final class SiblingRegisteredRector extends AbstractRector
+{
+    public function getRuleDefinition(): RuleDefinition
+    {
+        return new RuleDefinition('Rule registered in a sibling package config', [new CodeSample('before', 'after')]);
+    }
+
+    public function getNodeTypes(): array
+    {
+        return [Node::class];
+    }
+
+    public function refactor(Node $node): ?Node
+    {
+        return null;
+    }
+}
diff --git a/utils/phpstan/tests/Rule/RegisterRectorRule/Source/SkipDeprecatedRector.php b/utils/phpstan/tests/Rule/RegisterRectorRule/Source/SkipDeprecatedRector.php
new file mode 100644
index 00000000000..75cd492802a
--- /dev/null
+++ b/utils/phpstan/tests/Rule/RegisterRectorRule/Source/SkipDeprecatedRector.php
@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule\Source;
+
+use PhpParser\Node;
+use Rector\Configuration\Deprecation\Contract\DeprecatedInterface;
+use Rector\Rector\AbstractRector;
+use Rector\RuleDoc\CodeSample\CodeSample;
+use Rector\RuleDoc\RuleDefinition;
+
+final class SkipDeprecatedRector extends AbstractRector implements DeprecatedInterface
+{
+    public function getRuleDefinition(): RuleDefinition
+    {
+        return new RuleDefinition('Deprecated rule', [new CodeSample('before', 'after')]);
+    }
+
+    public function getNodeTypes(): array
+    {
+        return [Node::class];
+    }
+
+    public function refactor(Node $node): ?Node
+    {
+        return null;
+    }
+}
diff --git a/utils/phpstan/tests/Rule/RegisterRectorRule/Source/UnregisteredConfigurableRector.php b/utils/phpstan/tests/Rule/RegisterRectorRule/Source/UnregisteredConfigurableRector.php
new file mode 100644
index 00000000000..2f259ed9c27
--- /dev/null
+++ b/utils/phpstan/tests/Rule/RegisterRectorRule/Source/UnregisteredConfigurableRector.php
@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule\Source;
+
+use PhpParser\Node;
+use Rector\Contract\Rector\ConfigurableRectorInterface;
+use Rector\Rector\AbstractRector;
+use Rector\RuleDoc\CodeSample\CodeSample;
+use Rector\RuleDoc\RuleDefinition;
+
+final class UnregisteredConfigurableRector extends AbstractRector implements ConfigurableRectorInterface
+{
+    public function getRuleDefinition(): RuleDefinition
+    {
+        return new RuleDefinition('Configurable rule', [new CodeSample('before', 'after')]);
+    }
+
+    public function getNodeTypes(): array
+    {
+        return [Node::class];
+    }
+
+    public function refactor(Node $node): ?Node
+    {
+        return null;
+    }
+
+    public function configure(array $configuration): void
+    {
+    }
+}
diff --git a/utils/phpstan/tests/Rule/RegisterRectorRule/Source/UnregisteredRector.php b/utils/phpstan/tests/Rule/RegisterRectorRule/Source/UnregisteredRector.php
new file mode 100644
index 00000000000..5dcdf87b6c1
--- /dev/null
+++ b/utils/phpstan/tests/Rule/RegisterRectorRule/Source/UnregisteredRector.php
@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule\Source;
+
+use PhpParser\Node;
+use Rector\Rector\AbstractRector;
+use Rector\RuleDoc\CodeSample\CodeSample;
+use Rector\RuleDoc\RuleDefinition;
+
+final class UnregisteredRector extends AbstractRector
+{
+    public function getRuleDefinition(): RuleDefinition
+    {
+        return new RuleDefinition('Unregistered rule', [new CodeSample('before', 'after')]);
+    }
+
+    public function getNodeTypes(): array
+    {
+        return [Node::class];
+    }
+
+    public function refactor(Node $node): ?Node
+    {
+        return null;
+    }
+}
diff --git a/utils/phpstan/tests/Rule/RegisterRectorRule/config-sibling/sibling_set.php b/utils/phpstan/tests/Rule/RegisterRectorRule/config-sibling/sibling_set.php
new file mode 100644
index 00000000000..5fc6eb062c9
--- /dev/null
+++ b/utils/phpstan/tests/Rule/RegisterRectorRule/config-sibling/sibling_set.php
@@ -0,0 +1,8 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule\Source\SiblingRegisteredRector;
+
+// mimics a sibling extension package config set
+return [SiblingRegisteredRector::class];
diff --git a/utils/phpstan/tests/Rule/RegisterRectorRule/config/some_set.php b/utils/phpstan/tests/Rule/RegisterRectorRule/config/some_set.php
new file mode 100644
index 00000000000..f061ef2e627
--- /dev/null
+++ b/utils/phpstan/tests/Rule/RegisterRectorRule/config/some_set.php
@@ -0,0 +1,8 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Utils\PHPStan\Tests\Rule\RegisterRectorRule\Source\RegisteredRector;
+
+// mimics a set/level config; the rule only checks the "::class" reference is present
+return [RegisteredRector::class];