diff --git a/src/DI/Container.php b/src/DI/Container.php
index b949492c3..53b4a6765 100644
--- a/src/DI/Container.php
+++ b/src/DI/Container.php
@@ -140,6 +140,23 @@ public function get($name, $useProxy = false)
         throw new NotFoundException("No entry or class found for '$name'");
     }
 
+    /**
+     * Performs injection on an existing instance
+     *
+     * @param object $instance Object to perform injection upon
+     * @throws InvalidArgumentException
+     * @throws DependencyException
+     * @return object $instance
+     */
+    public function inject($instance)
+    {
+        $className = get_class($instance);
+        $definition = $this->definitionManager->getDefinition($className);
+
+        $instance = $this->factory->injectInstance($definition, $instance);
+        return $instance;
+    }
+
     /**
      * Define an object or a value in the container
      *
diff --git a/src/DI/Factory.php b/src/DI/Factory.php
index 36ac90fb5..40ca0a848 100644
--- a/src/DI/Factory.php
+++ b/src/DI/Factory.php
@@ -75,6 +75,34 @@ public function createInstance(ClassDefinition $classDefinition)
         return $instance;
     }
 
+    /**
+     * {@inheritdoc}
+     * @throws DependencyException
+     * @throws \DI\Definition\Exception\DefinitionException
+    */
+    public function injectInstance(ClassDefinition $classDefinition, $instance)
+    {
+        try {
+            // Property injections
+            foreach ($classDefinition->getPropertyInjections() as $propertyInjection) {
+                $this->injectProperty($instance, $propertyInjection);
+            }
+
+            // Method injections
+            foreach ($classDefinition->getMethodInjections() as $methodInjection) {
+                $this->injectMethod($instance, $methodInjection);
+            }
+        } catch (DependencyException $e) {
+            throw $e;
+        } catch (DefinitionException $e) {
+            throw $e;
+        } catch (NotFoundException $e) {
+            throw new DependencyException("Error while injecting dependencies into " . $classDefinition->getClassName() . ": " . $e->getMessage(), 0, $e);
+        }
+
+        return $instance;
+    }
+
     /**
      * Creates an instance and inject dependencies through the constructor
      *
diff --git a/src/DI/FactoryInterface.php b/src/DI/FactoryInterface.php
index 8621a0454..9e7bfc144 100644
--- a/src/DI/FactoryInterface.php
+++ b/src/DI/FactoryInterface.php
@@ -27,5 +27,5 @@ interface FactoryInterface
      * @return object The instance
      */
     function createInstance(ClassDefinition $classDefinition);
-
+    function injectInstance(ClassDefinition $classDefinition, $instance);
 }
diff --git a/tests/IntegrationTests/DI/InjectionTest.php b/tests/IntegrationTests/DI/InjectionTest.php
index b410b5a59..6ecb02e74 100644
--- a/tests/IntegrationTests/DI/InjectionTest.php
+++ b/tests/IntegrationTests/DI/InjectionTest.php
@@ -14,6 +14,8 @@
 use DI\Scope;
 use DI\Container;
 use IntegrationTests\DI\Fixtures\Class1;
+use IntegrationTests\DI\Fixtures\Class2;
+use IntegrationTests\DI\Fixtures\Implementation1;
 use IntegrationTests\DI\Fixtures\LazyDependency;
 
 /**
@@ -167,6 +169,33 @@ public function testPropertyInjection($type, Container $container)
         $this->assertTrue($proxy->isProxyInitialized());
     }
 
+    /**
+     * @dataProvider containerProvider
+     */
+    public function testPropertyInjectionExistingObject($type, Container $container)
+    {
+        // Only constructor injection with reflection
+        if ($type == self::DEFINITION_REFLECTION) {
+            return;
+        }
+        /** @var $class1 Class1 */
+        $class1 = new Class1(new Class2(), new Implementation1());
+        $container->inject($class1);
+        $this->assertInstanceOf('IntegrationTests\DI\Fixtures\Class2', $class1->property1);
+        $this->assertInstanceOf('IntegrationTests\DI\Fixtures\Implementation1', $class1->property2);
+        $this->assertInstanceOf('IntegrationTests\DI\Fixtures\Class2', $class1->property3);
+        $this->assertEquals('bar', $class1->property4);
+        // Lazy injection
+        /** @var LazyDependency|\ProxyManager\Proxy\LazyLoadingInterface $proxy */
+        $proxy = $class1->property5;
+        $this->assertInstanceOf('IntegrationTests\DI\Fixtures\LazyDependency', $proxy);
+        $this->assertInstanceOf('ProxyManager\Proxy\LazyLoadingInterface', $proxy);
+        $this->assertFalse($proxy->isProxyInitialized());
+        // Correct proxy resolution
+        $this->assertTrue($proxy->getValue());
+        $this->assertTrue($proxy->isProxyInitialized());
+    }
+
     /**
      * @dataProvider containerProvider
      */
@@ -193,6 +222,33 @@ public function testMethodInjection($type, Container $container)
         $this->assertTrue($proxy->isProxyInitialized());
     }
 
+    /**
+     * @dataProvider containerProvider
+     */
+    public function testMethodInjectionExistingObject($type, Container $container)
+    {
+        // Only constructor injection with reflection
+        if ($type == self::DEFINITION_REFLECTION) {
+            return;
+        }
+        /** @var $class1 Class1 */
+        $class1 = new Class1(new Class2(), new Implementation1());
+        $container->inject($class1);
+        $this->assertInstanceOf('IntegrationTests\DI\Fixtures\Class2', $class1->method1Param1);
+        $this->assertInstanceOf('IntegrationTests\DI\Fixtures\Implementation1', $class1->method2Param1);
+        $this->assertInstanceOf('IntegrationTests\DI\Fixtures\Class2', $class1->method3Param1);
+        $this->assertEquals('bar', $class1->method3Param2);
+        $this->assertInstanceOf('IntegrationTests\DI\Fixtures\LazyDependency', $class1->method4Param1);
+        $this->assertInstanceOf('ProxyManager\Proxy\LazyLoadingInterface', $class1->method4Param1);
+        // Lazy injection
+        /** @var LazyDependency|\ProxyManager\Proxy\LazyLoadingInterface $proxy */
+        $proxy = $class1->method4Param1;
+        $this->assertFalse($proxy->isProxyInitialized());
+        // Correct proxy resolution
+        $this->assertTrue($proxy->getValue());
+        $this->assertTrue($proxy->isProxyInitialized());
+    }
+
     /**
      * @dataProvider containerProvider
      */
diff --git a/tests/UnitTests/DI/ContainerTest.php b/tests/UnitTests/DI/ContainerTest.php
index 6227f9c90..1c3b22f87 100644
--- a/tests/UnitTests/DI/ContainerTest.php
+++ b/tests/UnitTests/DI/ContainerTest.php
@@ -152,6 +152,29 @@ public function testGetNonStringParameter()
         $container->get(new stdClass());
     }
 
+    /**
+     * Test that injecting an existing object returns the same reference to that object
+     */
+    public function testInjectMaintainsReferentialEquality()
+    {
+        $container = new Container();
+        $instance = new stdClass();
+        $result = $container->inject($instance);
+
+        $this->assertSame($instance, $result);
+    }
+
+    /**
+     * Test that injection on null yields null
+     */
+    public function testInjectNull()
+    {
+        $container = new Container();
+        $result = $container->inject(null);
+
+        $this->assertEquals($result, null);
+    }
+
     /**
      * We should be able to set a null value
      * @see https://github.com/mnapoli/PHP-DI/issues/79