Fast and lightweight JavaScript game engine built on WebGL and glTF
Orx: Portable Game Engine
KlayGE is a cross-platform open source game engine
A cross-platform 2D game engine
Multi-platform game engine similar to old Megaman with a stage editor
Cross platform 2D/3D game engine written in C++11 & OpenGL ES 2/3
A generic 2D engine for any kind of game
A Simple Game Engine
A very small multi-platform game engine for creating desktop games.