diff --git a/phpstan-baseline.neon b/phpstan-baseline.neon
index 7c8ec81ae84..3a4b45179db 100644
--- a/phpstan-baseline.neon
+++ b/phpstan-baseline.neon
@@ -170,6 +170,16 @@ parameters:
 			count: 1
 			path: src/Proxy/ProxyFactory.php
 
+		-
+			message: "#^Call to an undefined method ReflectionClass\\<object\\>\\:\\:newLazyGhost\\(\\)\\.$#"
+			count: 1
+			path: src/Proxy/ProxyFactory.php
+
+		-
+			message: "#^Call to an undefined method ReflectionProperty\\:\\:setRawValueWithoutLazyInitialization\\(\\)\\.$#"
+			count: 1
+			path: src/Proxy/ProxyFactory.php
+
 		-
 			message: "#^Call to an undefined static method Doctrine\\\\ORM\\\\Proxy\\\\ProxyFactory\\:\\:createLazyGhost\\(\\)\\.$#"
 			count: 1
diff --git a/src/Configuration.php b/src/Configuration.php
index b30764eb2b9..dfd56a5640f 100644
--- a/src/Configuration.php
+++ b/src/Configuration.php
@@ -30,6 +30,8 @@
 use function is_a;
 use function strtolower;
 
+use const PHP_VERSION_ID;
+
 /**
  * Configuration container for all configuration options of Doctrine.
  * It combines all configuration options from DBAL & ORM.
@@ -595,6 +597,20 @@ public function setSchemaIgnoreClasses(array $schemaIgnoreClasses): void
         $this->attributes['schemaIgnoreClasses'] = $schemaIgnoreClasses;
     }
 
+    public function isLazyProxyEnabled(): bool
+    {
+        return $this->attributes['lazyProxy'] ?? false;
+    }
+
+    public function setLazyProxyEnabled(bool $lazyProxy): void
+    {
+        if (PHP_VERSION_ID < 80400) {
+            throw new LogicException('Lazy loading proxies require PHP 8.4 or higher.');
+        }
+
+        $this->attributes['lazyProxy'] = $lazyProxy;
+    }
+
     /**
      * To be deprecated in 3.1.0
      *
diff --git a/src/Proxy/ProxyFactory.php b/src/Proxy/ProxyFactory.php
index b2d114a6698..4cb03456d2c 100644
--- a/src/Proxy/ProxyFactory.php
+++ b/src/Proxy/ProxyFactory.php
@@ -163,8 +163,43 @@ public function __construct(
      * @param class-string $className
      * @param array<mixed> $identifier
      */
-    public function getProxy(string $className, array $identifier): InternalProxy
+    public function getProxy(string $className, array $identifier): object
     {
+        if ($this->em->getConfiguration()->isLazyProxyEnabled()) {
+            $classMetadata   = $this->em->getClassMetadata($className);
+            $entityPersister = $this->uow->getEntityPersister($className);
+
+            $proxy = $classMetadata->reflClass->newLazyGhost(static function ($object) use ($identifier, $entityPersister): void {
+                $entityPersister->loadById($identifier, $object);
+            });
+
+            foreach ($identifier as $idField => $value) {
+                $classMetadata->reflFields[$idField]->setRawValueWithoutLazyInitialization($proxy, $value);
+            }
+
+            // todo: this skipLazyInitialization for properites calculation must be moved into ClassMetadata partially
+            $identifiers = array_flip($classMetadata->getIdentifierFieldNames());
+            $filter      = ReflectionProperty::IS_PUBLIC | ReflectionProperty::IS_PROTECTED | ReflectionProperty::IS_PRIVATE;
+            $reflector   = $classMetadata->getReflectionClass();
+
+            while ($reflector) {
+                foreach ($reflector->getProperties($filter) as $property) {
+                    $name = $property->name;
+
+                    if ($property->isStatic() || (($classMetadata->hasField($name) || $classMetadata->hasAssociation($name)) && ! isset($identifiers[$name]))) {
+                        continue;
+                    }
+
+                    $property->skipLazyInitialization($proxy);
+                }
+
+                $filter    = ReflectionProperty::IS_PRIVATE;
+                $reflector = $reflector->getParentClass();
+            }
+
+            return $proxy;
+        }
+
         $proxyFactory = $this->proxyFactories[$className] ?? $this->getProxyFactory($className);
 
         return $proxyFactory($identifier);
@@ -182,6 +217,10 @@ public function getProxy(string $className, array $identifier): InternalProxy
      */
     public function generateProxyClasses(array $classes, string|null $proxyDir = null): int
     {
+        if ($this->em->getConfiguration()->isLazyProxyEnabled()) {
+            return 0;
+        }
+
         $generated = 0;
 
         foreach ($classes as $class) {
diff --git a/src/UnitOfWork.php b/src/UnitOfWork.php
index 85a33620aa8..ba4eefc9e04 100644
--- a/src/UnitOfWork.php
+++ b/src/UnitOfWork.php
@@ -49,6 +49,7 @@
 use Doctrine\Persistence\PropertyChangedListener;
 use Exception;
 use InvalidArgumentException;
+use ReflectionObject;
 use RuntimeException;
 use Stringable;
 use Throwable;
@@ -64,6 +65,7 @@
 use function array_values;
 use function assert;
 use function current;
+use function get_class;
 use function get_debug_type;
 use function implode;
 use function in_array;
@@ -2383,7 +2385,11 @@ public function createEntity(string $className, array $data, array &$hints = [])
             }
 
             if ($this->isUninitializedObject($entity)) {
-                $entity->__setInitialized(true);
+                if ($this->em->getConfiguration()->isLazyProxyEnabled()) {
+                    $class->reflClass->markLazyObjectAsInitialized($entity);
+                } else {
+                    $entity->__setInitialized(true);
+                }
             } else {
                 if (
                     ! isset($hints[Query::HINT_REFRESH])
@@ -3040,6 +3046,11 @@ public function initializeObject(object $obj): void
         if ($obj instanceof PersistentCollection) {
             $obj->initialize();
         }
+
+        if ($this->em->getConfiguration()->isLazyProxyEnabled()) {
+            $reflection = new ReflectionObject($obj);
+            $reflection->initializeLazyObject($obj);
+        }
     }
 
     /**
@@ -3049,6 +3060,10 @@ public function initializeObject(object $obj): void
      */
     public function isUninitializedObject(mixed $obj): bool
     {
+        if ($this->em->getConfiguration()->isLazyProxyEnabled() && ! ($obj instanceof Collection)) {
+            return $this->em->getClassMetadata(get_class($obj))->reflClass->isUninitializedLazyObject($obj);
+        }
+
         return $obj instanceof InternalProxy && ! $obj->__isInitialized();
     }
 
diff --git a/tests/Tests/ORM/Functional/BasicFunctionalTest.php b/tests/Tests/ORM/Functional/BasicFunctionalTest.php
index fe03a864060..7758c5baf2d 100644
--- a/tests/Tests/ORM/Functional/BasicFunctionalTest.php
+++ b/tests/Tests/ORM/Functional/BasicFunctionalTest.php
@@ -557,7 +557,7 @@ public function testSetToOneAssociationWithGetReference(): void
         $this->_em->persist($article);
         $this->_em->flush();
 
-        self::assertFalse($userRef->__isInitialized());
+        self::assertTrue($this->isUninitializedObject($userRef));
 
         $this->_em->clear();
 
@@ -592,7 +592,7 @@ public function testAddToToManyAssociationWithGetReference(): void
         $this->_em->persist($user);
         $this->_em->flush();
 
-        self::assertFalse($groupRef->__isInitialized());
+        self::assertTrue($this->isUninitializedObject($groupRef));
 
         $this->_em->clear();
 
@@ -940,8 +940,7 @@ public function testManyToOneFetchModeQuery(): void
                              ->setParameter(1, $article->id)
                              ->setFetchMode(CmsArticle::class, 'user', ClassMetadata::FETCH_EAGER)
                              ->getSingleResult();
-        self::assertInstanceOf(InternalProxy::class, $article->user, 'It IS a proxy, ...');
-        self::assertFalse($this->isUninitializedObject($article->user), '...but its initialized!');
+        self::assertFalse($this->isUninitializedObject($article->user));
         $this->assertQueryCount(2);
     }
 
diff --git a/tests/Tests/ORM/Functional/ProxiesLikeEntitiesTest.php b/tests/Tests/ORM/Functional/ProxiesLikeEntitiesTest.php
index 0cc8776ba50..df8ca3b9187 100644
--- a/tests/Tests/ORM/Functional/ProxiesLikeEntitiesTest.php
+++ b/tests/Tests/ORM/Functional/ProxiesLikeEntitiesTest.php
@@ -34,6 +34,10 @@ protected function setUp(): void
     {
         parent::setUp();
 
+        if ($this->_em->getConfiguration()->isLazyProxyEnabled()) {
+            self::markTestSkipped('This test is not applicable when lazy proxy is enabled.');
+        }
+
         $this->createSchemaForModels(
             CmsUser::class,
             CmsTag::class,
diff --git a/tests/Tests/ORM/Functional/ReferenceProxyTest.php b/tests/Tests/ORM/Functional/ReferenceProxyTest.php
index 55f65956757..a9e9d1952a3 100644
--- a/tests/Tests/ORM/Functional/ReferenceProxyTest.php
+++ b/tests/Tests/ORM/Functional/ReferenceProxyTest.php
@@ -248,7 +248,6 @@ public function testCommonPersistenceProxy(): void
         assert($entity instanceof ECommerceProduct);
         $className = DefaultProxyClassNameResolver::getClass($entity);
 
-        self::assertInstanceOf(InternalProxy::class, $entity);
         self::assertTrue($this->isUninitializedObject($entity));
         self::assertEquals(ECommerceProduct::class, $className);
 
@@ -257,7 +256,7 @@ public function testCommonPersistenceProxy(): void
         $proxyFileName = $this->_em->getConfiguration()->getProxyDir() . DIRECTORY_SEPARATOR . str_replace('\\', '', $restName) . '.php';
         self::assertTrue(file_exists($proxyFileName), 'Proxy file name cannot be found generically.');
 
-        $entity->__load();
+        $this->initializeObject($entity);
         self::assertFalse($this->isUninitializedObject($entity));
     }
 }
diff --git a/tests/Tests/ORM/Functional/SecondLevelCacheQueryCacheTest.php b/tests/Tests/ORM/Functional/SecondLevelCacheQueryCacheTest.php
index a3350aa5e6c..ae0a36b0f92 100644
--- a/tests/Tests/ORM/Functional/SecondLevelCacheQueryCacheTest.php
+++ b/tests/Tests/ORM/Functional/SecondLevelCacheQueryCacheTest.php
@@ -11,7 +11,6 @@
 use Doctrine\ORM\Cache\Exception\CacheException;
 use Doctrine\ORM\Cache\QueryCacheEntry;
 use Doctrine\ORM\Cache\QueryCacheKey;
-use Doctrine\ORM\Proxy\InternalProxy;
 use Doctrine\ORM\Query;
 use Doctrine\ORM\Query\ResultSetMapping;
 use Doctrine\Tests\Models\Cache\Attraction;
@@ -939,7 +938,6 @@ public function testResolveAssociationCacheEntry(): void
         self::assertNotNull($state1->getCountry());
         $this->assertQueryCount(1);
         self::assertInstanceOf(State::class, $state1);
-        self::assertInstanceOf(InternalProxy::class, $state1->getCountry());
         self::assertEquals($countryName, $state1->getCountry()->getName());
         self::assertEquals($stateId, $state1->getId());
 
@@ -957,7 +955,6 @@ public function testResolveAssociationCacheEntry(): void
         self::assertNotNull($state2->getCountry());
         $this->assertQueryCount(0);
         self::assertInstanceOf(State::class, $state2);
-        self::assertInstanceOf(InternalProxy::class, $state2->getCountry());
         self::assertEquals($countryName, $state2->getCountry()->getName());
         self::assertEquals($stateId, $state2->getId());
     }
@@ -1031,7 +1028,6 @@ public function testResolveToManyAssociationCacheEntry(): void
 
         $this->assertQueryCount(1);
         self::assertInstanceOf(State::class, $state1);
-        self::assertInstanceOf(InternalProxy::class, $state1->getCountry());
         self::assertInstanceOf(City::class, $state1->getCities()->get(0));
         self::assertInstanceOf(State::class, $state1->getCities()->get(0)->getState());
         self::assertSame($state1, $state1->getCities()->get(0)->getState());
@@ -1048,7 +1044,6 @@ public function testResolveToManyAssociationCacheEntry(): void
 
         $this->assertQueryCount(0);
         self::assertInstanceOf(State::class, $state2);
-        self::assertInstanceOf(InternalProxy::class, $state2->getCountry());
         self::assertInstanceOf(City::class, $state2->getCities()->get(0));
         self::assertInstanceOf(State::class, $state2->getCities()->get(0)->getState());
         self::assertSame($state2, $state2->getCities()->get(0)->getState());
diff --git a/tests/Tests/ORM/Functional/SecondLevelCacheRepositoryTest.php b/tests/Tests/ORM/Functional/SecondLevelCacheRepositoryTest.php
index 7ed7732526c..5b8919af6f5 100644
--- a/tests/Tests/ORM/Functional/SecondLevelCacheRepositoryTest.php
+++ b/tests/Tests/ORM/Functional/SecondLevelCacheRepositoryTest.php
@@ -198,8 +198,6 @@ public function testRepositoryCacheFindAllToOneAssociation(): void
         self::assertInstanceOf(State::class, $entities[1]);
         self::assertInstanceOf(Country::class, $entities[0]->getCountry());
         self::assertInstanceOf(Country::class, $entities[0]->getCountry());
-        self::assertInstanceOf(InternalProxy::class, $entities[0]->getCountry());
-        self::assertInstanceOf(InternalProxy::class, $entities[1]->getCountry());
 
         // load from cache
         $this->getQueryLog()->reset()->enable();
@@ -212,8 +210,6 @@ public function testRepositoryCacheFindAllToOneAssociation(): void
         self::assertInstanceOf(State::class, $entities[1]);
         self::assertInstanceOf(Country::class, $entities[0]->getCountry());
         self::assertInstanceOf(Country::class, $entities[1]->getCountry());
-        self::assertInstanceOf(InternalProxy::class, $entities[0]->getCountry());
-        self::assertInstanceOf(InternalProxy::class, $entities[1]->getCountry());
 
         // invalidate cache
         $this->_em->persist(new State('foo', $this->_em->find(Country::class, $this->countries[0]->getId())));
@@ -231,8 +227,6 @@ public function testRepositoryCacheFindAllToOneAssociation(): void
         self::assertInstanceOf(State::class, $entities[1]);
         self::assertInstanceOf(Country::class, $entities[0]->getCountry());
         self::assertInstanceOf(Country::class, $entities[1]->getCountry());
-        self::assertInstanceOf(InternalProxy::class, $entities[0]->getCountry());
-        self::assertInstanceOf(InternalProxy::class, $entities[1]->getCountry());
 
         // load from cache
         $this->getQueryLog()->reset()->enable();
@@ -245,7 +239,5 @@ public function testRepositoryCacheFindAllToOneAssociation(): void
         self::assertInstanceOf(State::class, $entities[1]);
         self::assertInstanceOf(Country::class, $entities[0]->getCountry());
         self::assertInstanceOf(Country::class, $entities[1]->getCountry());
-        self::assertInstanceOf(InternalProxy::class, $entities[0]->getCountry());
-        self::assertInstanceOf(InternalProxy::class, $entities[1]->getCountry());
     }
 }
diff --git a/tests/Tests/ORM/Functional/Ticket/DDC1238Test.php b/tests/Tests/ORM/Functional/Ticket/DDC1238Test.php
index 7a3cce370fd..72dc3496e74 100644
--- a/tests/Tests/ORM/Functional/Ticket/DDC1238Test.php
+++ b/tests/Tests/ORM/Functional/Ticket/DDC1238Test.php
@@ -57,11 +57,11 @@ public function testIssueProxyClear(): void
 
         $user2 = $this->_em->getReference(DDC1238User::class, $userId);
 
-        //$user->__load();
+        //$this->initializeObject($user);
 
         self::assertIsInt($user->getId(), 'Even if a proxy is detached, it should still have an identifier');
 
-        $user2->__load();
+        $this->initializeObject($user2);
 
         self::assertIsInt($user2->getId(), 'The managed instance still has an identifier');
     }
diff --git a/tests/Tests/ORM/Functional/Ticket/GH10808Test.php b/tests/Tests/ORM/Functional/Ticket/GH10808Test.php
index 0e893233442..49334b53bcd 100644
--- a/tests/Tests/ORM/Functional/Ticket/GH10808Test.php
+++ b/tests/Tests/ORM/Functional/Ticket/GH10808Test.php
@@ -49,18 +49,11 @@ public function testDQLDeferredEagerLoad(): void
         // Clear the EM to prevent the recovery of the loaded instance, which would otherwise result in a proxy.
         $this->_em->clear();
 
+        self::assertTrue($this->_em->getUnitOfWork()->isUninitializedObject($deferredLoadResult->child));
+
         $eagerLoadResult = $query->setHint(UnitOfWork::HINT_DEFEREAGERLOAD, false)->getSingleResult();
 
-        self::assertNotEquals(
-            GH10808AppointmentChild::class,
-            get_class($deferredLoadResult->child),
-            '$deferredLoadResult->child should be a proxy',
-        );
-        self::assertEquals(
-            GH10808AppointmentChild::class,
-            get_class($eagerLoadResult->child),
-            '$eagerLoadResult->child should not be a proxy',
-        );
+        self::assertFalse($this->_em->getUnitOfWork()->isUninitializedObject($eagerLoadResult->child));
     }
 }
 
diff --git a/tests/Tests/OrmFunctionalTestCase.php b/tests/Tests/OrmFunctionalTestCase.php
index edec9ca261e..7bee4958914 100644
--- a/tests/Tests/OrmFunctionalTestCase.php
+++ b/tests/Tests/OrmFunctionalTestCase.php
@@ -22,6 +22,7 @@
 use Doctrine\ORM\Exception\ORMException;
 use Doctrine\ORM\Mapping\ClassMetadata;
 use Doctrine\ORM\Mapping\Driver\AttributeDriver;
+use Doctrine\ORM\Proxy\InternalProxy;
 use Doctrine\ORM\Tools\DebugUnitOfWorkListener;
 use Doctrine\ORM\Tools\SchemaTool;
 use Doctrine\ORM\Tools\ToolsException;
@@ -193,6 +194,7 @@
 use function var_export;
 
 use const PHP_EOL;
+use const PHP_VERSION_ID;
 
 /**
  * Base testcase class for all functional ORM testcases.
@@ -941,6 +943,12 @@ protected function getEntityManager(
             $this->isSecondLevelCacheEnabled = true;
         }
 
+        $enableLazyProxy = getenv('ENABLE_LAZY_PROXY');
+
+        if (PHP_VERSION_ID >= 80400 && $enableLazyProxy) {
+            $config->setLazyProxyEnabled(true);
+        }
+
         $config->setMetadataDriverImpl(
             $mappingDriver ?? new AttributeDriver([
                 realpath(__DIR__ . '/Models/Cache'),
@@ -1118,4 +1126,9 @@ final protected function isUninitializedObject(object $entity): bool
     {
         return $this->_em->getUnitOfWork()->isUninitializedObject($entity);
     }
+
+    final protected function initializeObject(object $entity): void
+    {
+        $this->_em->getUnitOfWork()->initializeObject($entity);
+    }
 }