Direct3D is part of Microsoft's DirectX API. Direct3D is only for use in Microsoft's various Windows operating systems (Windows 95 and above) and the Xbox. Direct3D is used to render three dimensional graphics in applications where top performance is important, such as games. Direct3D also allows applications to run fullscreen instead of embedded in a window, though they can still run in a window if programmed for that feature. Direct3D uses hardware acceleration if it is available on the graphic board.

Direct3D is a 3D API. That is, it contains many commands for 3D rendering, but contains few commands for rendering 2D graphics. Direct3D offers little software emulation for features not available in hardware. For example, if a program programmed using Direct3D requires pixel shaders and the graphics card on the user's computer does not support that feature, Direct3D will not emulate it. The program will most likely exit with an error message.

Direct3D's main competitor is OpenGL. There are numerous features and issues that proponents for either API disagree over. Some issues include ease of use, portability, API regulation and speed.

As of DirectX verion 8.1, Direct3D contained many very powerful 3D graphics features, such as vertex shaders, pixel shaders, fog, bump mapping and texture mapping. Microsoft continually updates Direct3D with the latest technology available on 3D graphics cards.

As of DirectX version 8.0, Direct3D was rolled up into a package called DirectX Graphics. DirectX Graphics was meant to be a combination of DirectDraw and Direct3D, but in reality was just Direct3D with a few DirectDraw commands added. Most users still refer to DirectX Graphics as Direct3D.

There are several bugs when running a Direct3D application under Windows Server 2003.