Managed DirectX (short MDX) is an API to DirectX programming under .NET developed by Microsoft. MDX can be used from any language under the .NET runtime (an advantage of the CLR), but mostly (C#) is used.

MDX can be used to develop multimedia and interactive applications (e.g. games). Enabling high performance graphical representation and enabling the programmer to make use of modern graphical hardware while working inside the .Net framework.

Managed DirectX was first released in 2002 to allow less experienced programmers access to the DirectX API through the .NET framework. The Managed DirectX SDK allows developers access to numerous classes which allow the rendering of 3D graphics (Direct3D) and the other DirectX API's in a much easier, object-oriented manner. MDX is currently deprecated in favour of XNA Game Studio Express, however a more direct successor is the open-source SlimDX.