Godot is a powerful cross-platform game engine
Xash3D FWGS engine
A complete 3-D game development suite written in Java
Cocos simplifies game creation and distribution with Cocos Creator
Voxel game-creation platform with easy modding and game creation
Powerful, mature open-source cross-platform game engine for Python
The Ren'Py Visual Novel Engine
Cross-platform game engine in Rust
Cross-Platform C++ 2D/3D game engine
Multi Theft Auto is a game engine
The flexible game engine
3D Procedural Game Engine Using OpenGL
Cross-platform 2D game engine focused on ultimate productivity
Recreation of the classic Grand Theft Auto III game executable
Open source clone of the Age of Empires II engine
Cross-platform 2D and 3D game engine with modular architecture
Descent 3 by Outrage Entertainment
A completely free, open-source, 2D game engine
The HTML5 Creation Engine
The ioquake3 community effort to continue supporting/developing id's
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
KorGE Game Engine. Multiplatform Kotlin Game Engine & Korlibs
Free game engine for development of desktop, mobile, and web games
The game engine for everyone
A game engine powered by python and panda3d