Godot is a powerful cross-platform game engine
Multi Theft Auto is a game engine
The Ren'Py Visual Novel Engine
Cocos simplifies game creation and distribution with Cocos Creator
Open game and rendering engine packed into a JavaScript framework
Xash3D FWGS engine
A complete 3-D game development suite written in Java
Real Time Strategy game engine supporting early Westwood classics
The game engine for everyone
Open source voxel game engine with support for survival and crafting
A game engine powered by python and panda3d
fheroes2 is a recreation of Heroes of Might and Magic II game engine
Voxel game-creation platform with easy modding and game creation
Fast and lightweight JavaScript game engine built on WebGL and glTF
3D Procedural Game Engine Using OpenGL
3D Game engine with editor
LayaAir is an open-source 2D/3D engine
Powerful, mature open-source cross-platform game engine for Python
Flax Engine, multi-platform 3D game engine
Solar2D Game Engine main repository (ex Corona SDK)
The ioquake3 community effort to continue supporting/developing id's
Cross-Platform C++ 2D/3D game engine
Magic Another Game Engine
A multi core friendly rigid body physics and collision detection lib
Free, cross-platform 2D game engine powered by Haxe and OpenFL