diff --git a/composer.json b/composer.json
index f103b8d46db5..97ff13111390 100644
--- a/composer.json
+++ b/composer.json
@@ -61,7 +61,8 @@
             "Rector\\PhpSpecToPHPUnit\\": "packages/PhpSpecToPHPUnit/src",
             "Rector\\Shopware\\": "packages/Shopware/src",
             "Rector\\NetteTesterToPHPUnit\\": "packages/NetteTesterToPHPUnit/src",
-            "Rector\\Nette\\": "packages/Nette/src"
+            "Rector\\Nette\\": "packages/Nette/src",
+            "Rector\\SOLID\\": "packages/SOLID/src"
         }
     },
     "autoload-dev": {
@@ -94,7 +95,8 @@
             "Rector\\PHPStanExtensions\\": "utils/PHPStanExtensions/src",
             "Rector\\Shopware\\Tests\\": "packages/Shopware/tests",
             "Rector\\NetteTesterToPHPUnit\\Tests\\": "packages/NetteTesterToPHPUnit/tests",
-            "Rector\\Nette\\Tests\\": "packages/Nette/tests"
+            "Rector\\Nette\\Tests\\": "packages/Nette/tests",
+            "Rector\\SOLID\\Tests\\": "packages/SOLID/tests"
         },
         "classmap": [
             "packages/Symfony/tests/Rector/FrameworkBundle/AbstractToConstructorInjectionRectorSource",
@@ -138,4 +140,4 @@
             "dev-master": "0.5-dev"
         }
     }
-}
+}
\ No newline at end of file
diff --git a/config/level/solid/solid.yaml b/config/level/solid/solid.yaml
new file mode 100644
index 000000000000..028ae61f9d4a
--- /dev/null
+++ b/config/level/solid/solid.yaml
@@ -0,0 +1,2 @@
+services:
+    Rector\SOLID\Rector\Class_\FinalizeClassesWithoutChildrenRector: ~
diff --git a/packages/NodeTypeResolver/src/Application/ClassLikeNodeCollector.php b/packages/NodeTypeResolver/src/Application/ClassLikeNodeCollector.php
index 038701cd3b1d..bce5851d4127 100644
--- a/packages/NodeTypeResolver/src/Application/ClassLikeNodeCollector.php
+++ b/packages/NodeTypeResolver/src/Application/ClassLikeNodeCollector.php
@@ -200,4 +200,9 @@ public function findClassesBySuffix(string $suffix): array
 
         return $classNodes;
     }
+
+    public function hasClassChildren(string $class): bool
+    {
+        return $this->findChildrenOfClass($class) !== [];
+    }
 }
diff --git a/packages/SOLID/src/Rector/Class_/FinalizeClassesWithoutChildrenRector.php b/packages/SOLID/src/Rector/Class_/FinalizeClassesWithoutChildrenRector.php
new file mode 100644
index 000000000000..391104068384
--- /dev/null
+++ b/packages/SOLID/src/Rector/Class_/FinalizeClassesWithoutChildrenRector.php
@@ -0,0 +1,99 @@
+<?php declare(strict_types=1);
+
+namespace Rector\SOLID\Rector\Class_;
+
+use Nette\Utils\Strings;
+use PhpParser\Node;
+use Rector\NodeTypeResolver\Application\ClassLikeNodeCollector;
+use Rector\Rector\AbstractRector;
+use Rector\RectorDefinition\CodeSample;
+use Rector\RectorDefinition\RectorDefinition;
+
+final class FinalizeClassesWithoutChildrenRector extends AbstractRector
+{
+    /**
+     * @var ClassLikeNodeCollector
+     */
+    private $classLikeNodeCollector;
+
+    public function __construct(ClassLikeNodeCollector $classLikeNodeCollector)
+    {
+        $this->classLikeNodeCollector = $classLikeNodeCollector;
+    }
+
+    public function getDefinition(): RectorDefinition
+    {
+        return new RectorDefinition('Finalize every class that has no children', [
+            new CodeSample(
+                <<<'CODE_SAMPLE'
+class FirstClass
+{
+}
+
+class SecondClass
+{
+}
+
+class ThirdClass extends SecondClass
+{
+}
+CODE_SAMPLE
+                ,
+                <<<'CODE_SAMPLE'
+final class FirstClass
+{
+}
+
+class SecondClass
+{
+}
+
+final class ThirdClass extends SecondClass
+{
+}
+CODE_SAMPLE
+            ),
+        ]);
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getNodeTypes(): array
+    {
+        return [Node\Stmt\Class_::class];
+    }
+
+    /**
+     * @param Node\Stmt\Class_ $node
+     */
+    public function refactor(Node $node): ?Node
+    {
+        if ($node->isFinal() || $node->isAbstract() || $node->isAnonymous()) {
+            return null;
+        }
+
+        if ($this->isDoctrineEntity($node)) {
+            return null;
+        }
+
+        /** @var string $class */
+        $class = $this->getName($node);
+        if ($this->classLikeNodeCollector->hasClassChildren($class)) {
+            return null;
+        }
+
+        $node->flags |= Node\Stmt\Class_::MODIFIER_FINAL;
+
+        return $node;
+    }
+
+    private function isDoctrineEntity(Node $node): bool
+    {
+        if ($node->getDocComment() === null) {
+            return false;
+        }
+
+        return Strings::contains($node->getDocComment()->getText(), 'Entity');
+    }
+}
diff --git a/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/FinalizeClassesWithoutChildrenRectorTest.php b/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/FinalizeClassesWithoutChildrenRectorTest.php
new file mode 100644
index 000000000000..b3af5f390823
--- /dev/null
+++ b/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/FinalizeClassesWithoutChildrenRectorTest.php
@@ -0,0 +1,23 @@
+<?php declare(strict_types=1);
+
+namespace Rector\SOLID\Tests\Rector\Class_\FinalizeClassesWithoutChildrenRector;
+
+use Rector\SOLID\Rector\Class_\FinalizeClassesWithoutChildrenRector;
+use Rector\Testing\PHPUnit\AbstractRectorTestCase;
+
+final class FinalizeClassesWithoutChildrenRectorTest extends AbstractRectorTestCase
+{
+    public function test(): void
+    {
+        $this->doTestFiles([
+            __DIR__ . '/Fixture/fixture.php.inc',
+            __DIR__ . '/Fixture/skip.php.inc',
+            __DIR__ . '/Fixture/entity.php.inc',
+        ]);
+    }
+
+    protected function getRectorClass(): string
+    {
+        return FinalizeClassesWithoutChildrenRector::class;
+    }
+}
diff --git a/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/Fixture/entity.php.inc b/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/Fixture/entity.php.inc
new file mode 100644
index 000000000000..cf09d3d4016d
--- /dev/null
+++ b/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/Fixture/entity.php.inc
@@ -0,0 +1,10 @@
+<?php
+
+namespace Rector\SOLID\Tests\Rector\Class_\FinalizeClassesWithoutChildrenRector\Fixture;
+
+/**
+ * @ORM\Entity
+ */
+class Product
+{
+}
diff --git a/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/Fixture/fixture.php.inc b/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/Fixture/fixture.php.inc
new file mode 100644
index 000000000000..d72e6cd805ec
--- /dev/null
+++ b/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/Fixture/fixture.php.inc
@@ -0,0 +1,35 @@
+<?php
+
+namespace Rector\SOLID\Tests\Rector\Class_\FinalizeClassesWithoutChildrenRector\Fixture;
+
+class FirstClass
+{
+}
+
+class SecondClass
+{
+}
+
+class ThirdClass extends SecondClass
+{
+}
+
+?>
+-----
+<?php
+
+namespace Rector\SOLID\Tests\Rector\Class_\FinalizeClassesWithoutChildrenRector\Fixture;
+
+final class FirstClass
+{
+}
+
+class SecondClass
+{
+}
+
+final class ThirdClass extends SecondClass
+{
+}
+
+?>
diff --git a/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/Fixture/skip.php.inc b/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/Fixture/skip.php.inc
new file mode 100644
index 000000000000..1416d9be18a6
--- /dev/null
+++ b/packages/SOLID/tests/Rector/Class_/FinalizeClassesWithoutChildrenRector/Fixture/skip.php.inc
@@ -0,0 +1,7 @@
+<?php
+
+namespace Rector\SOLID\Tests\Rector\Class_\FinalizeClassesWithoutChildrenRector\Fixture;
+
+abstract class SkipAbstractClass
+{
+}