XScreenSaver is a free screensaver for Unix-like operating systems that use the X Window System. It was developed by Jamie Zawinski and is under the MIT license.

The XScreenSaver is in particular the free Unix systems (GNU / Linux, etc.) spread, but the work environments KDE and GNOME own screensaver ( kscreensaver or gnome -screensaver ) have developed.

One reason for the popularity of the XScreenSaver is also possible for programmers to develop their own modules. So, for example, OpenGL-based animations like GLMatrix can be added. A management system allows configure the modules, for example, the speed at which the animations to be played. Some modules also handle image files or texts that are freely adjustable.

In addition to changing the screen contents, the current X session can be locked so that the user must enter his password to get back to the screen content.