Godot is a powerful cross-platform game engine
Solar2D Game Engine main repository (ex Corona SDK)
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
The flexible game engine
Open source voxel game engine with support for survival and crafting
Xash3D FWGS engine
Cocos simplifies game creation and distribution with Cocos Creator
Multi-platform 2D and 3D game engine
Fast and lightweight JavaScript game engine built on WebGL and glTF
Flax Engine, multi-platform 3D game engine
JavaScript-based game engine designed to empower developers
Cross-Platform C++ 2D/3D game engine
Cross-platform 2D and 3D game engine with modular architecture
V1, Mirror Classic. V2, Mirror Engine: Join Discord for access
Native Android app for Habitica
Game engine supporting many 3D/2D formats and graphic effects
Unicorn CPU emulator framework (ARM, AArch64, M68K, Mips, Sparc
A game engine with an emphasis on real-time cutting-edge solutions
An unofficial rules engine for the world's greatest card game
Voxel game-creation platform with easy modding and game creation
The game engine for everyone
GemRB is a portable open-source implementation of the Infinity Engine
A JavaScript engine optimized for running React Native
An OpenGL RTS game engine written in C
Simple and light-weight 3D game engine