Warzone 2100 is an open-source real-time strategy and real-time tactics hybrid computer game, originally developed by Pumpkin Studios and published by Eidos Interactive. It was originally released in 1999 for Microsoft Windows and PlayStation, and is now also available for macOS, FreeBSD, AmigaOS 4, AROS, MorphOS, Linux, NetBSD and OpenBSD.

While Warzone 2100 was developed and released as a proprietary commercial video game, on December 6, 2004, the source code and most of its data was released under the GNU GPL-2.0-or-later; the rest of the data followed on June 10, 2008.