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