A game engine powered by python and panda3d
Zig game engine & graphics toolkit
3D game engine/framework in C, with Luajit and Python bindings now
Game engine supporting many 3D/2D formats and graphic effects
Descent 3 by Outrage Entertainment
High performance UI layout library in C
GemRB is a portable open-source implementation of the Infinity Engine
2D JavaScript Physics Engine
A modern, cross-platform Quake game engine based on FitzQuake.
Orx: Data-Driven Game Engine
C++ lightweight cross-platform game engine
The multiplayer game engine
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
DOOM / Heretic / Hexen source port with enhanced graphics and UI
Opensource Game Studio
Web powered cross-platform 3D, WebXR game engine
Portable game engine with main focus on point-and-click adventures
scriptable game engine with built-in support for 2D graphics and sound
Multi-platform game engine similar to old Megaman with a stage editor
An advanced flexible game engine for Java.
Open Source 3D Game Engine
A generic 2D engine for any kind of game