X.Org Server(全称为X.Org Foundation Open Source Public Implementation of X11) 是X Window System的官方参考实作，它是开放源代码的自由软件。

这个项目由X.Org基金会运作，存放于freedesktop.org的主机上。

由于在XFree8***.4最终版本采用新许可证问题上的分歧，Xorg服务器的第一个版本X11R6.7.0从XFree86 4.4 RC2派生出来，并加入了X11R6.6的一些改动。许多原先XFree86的开发者加入了这个比XFree86更开放的项目。

X.Org Server is the free and open source implementation of the display server for the X Window System stewarded by the X.Org Foundation.

Implementations of the client side of the protocol are available e.g. in the form of Xlib and XCB.

The services with which the X.Org Foundation supports X Server include the packaging of the releases; certification (for a fee); evaluation of improvements to the code; developing the web site, and handling the distribution of monetary donations. The releases are coded, documented, and packaged by global developers.