Freedoom is a project aiming to create open content for the free and open source software Doom engine. The project distributes three IWAD files: the two single-player campaigns named Freedoom: Phase 1 and Freedoom: Phase 2, and FreeDM, which contains a collection of deathmatch levels.

The project presents itself as complementary to the free and open source code of the Doom engine released by id Software in 1997 under the GNU GPL license. The content is licensed under the permissive 3-clause BSD license. It allows custom levels and other customizations designed for Doom, Doom II or Final Doom (e.g. PWAD files) to be used with Freedoom.