Xonotic is an open-source, multiplayer first-person shooter built using a modified version of the Quake engine.

Xonotic is a fork of the source code used to build Nexuiz, another open-source first-person shooter built on the Quake engine. Community developers forked the source as a response to the original development leads of Nexuiz signing a deal with Illfonic to remake the game as a closed-source sci-fi shooter for Xbox Live Arcade, PlayStation Network, and PC that was released in 2012.

Weapon balance, art style, and other aspects of Nexuiz have been dramatically changed in Xonotic, though Xonotic is still considered to be an early project, with the most recent official released marked as version 0.6. Individuals wishing to contribute to the project can start by checking the message boards at the game's official site.