Godot is a powerful cross-platform game engine
The flexible game engine
Solar2D Game Engine main repository (ex Corona SDK)
An OpenGL RTS game engine written in C
Fast and lightweight JavaScript game engine built on WebGL and glTF
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
Cross-platform 2D and 3D game engine with modular architecture
A game engine powered by python and panda3d
Multi-platform 2D and 3D game engine
Cocos simplifies game creation and distribution with Cocos Creator
Cross-Platform C++ 2D/3D game engine
A game engine with an emphasis on real-time cutting-edge solutions
Zig game engine & graphics toolkit
Powerful, mature open-source cross-platform game engine for Python
Xash3D FWGS engine
The Ren'Py Visual Novel Engine
Open source clone of the Age of Empires II engine
GemRB is a portable open-source implementation of the Infinity Engine
Open-source engine for Heroes of Might and Magic III
A retro game engine for Python
Game engine supporting many 3D/2D formats and graphic effects
A complete 3-D game development suite written in Java
Open source voxel game engine with support for survival and crafting
Self-hosted game stream host for Moonlight
Multi Theft Auto is a game engine