Godot is a powerful cross-platform game engine
Solar2D Game Engine main repository (ex Corona SDK)
The flexible game engine
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
Multi-platform 2D and 3D game engine
Cocos simplifies game creation and distribution with Cocos Creator
Xash3D FWGS engine
Open source voxel game engine with support for survival and crafting
Fast and lightweight JavaScript game engine built on WebGL and glTF
Flax Engine, multi-platform 3D game engine
High-performance, privacy-focused browser built as a fork of Chromium
Cross-platform 2D and 3D game engine with modular architecture
An unofficial rules engine for the world's greatest card game
Native Android app for Habitica
Voxel game-creation platform with easy modding and game creation
Unicorn CPU emulator framework (ARM, AArch64, M68K, Mips, Sparc
Game engine supporting many 3D/2D formats and graphic effects
A game engine with an emphasis on real-time cutting-edge solutions
Zig game engine & graphics toolkit
The game engine for everyone
An OpenGL RTS game engine written in C
Simple and light-weight 3D game engine
GemRB is a portable open-source implementation of the Infinity Engine
A Minecraft Java Edition Launcher for Android and iOS
Satisfying monster shooter