Cross-Platform C++ 2D/3D game engine
Fast and lightweight JavaScript game engine built on WebGL and glTF
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Powerful, mature open-source cross-platform game engine for Python
LayaAir is an open-source 2D/3D engine
The Open Toolkit library is a fast, low-level C# wrapper for OpenGL
3D Procedural Game Engine Using OpenGL
3D game engine/framework in C, with Luajit and Python bindings now
Open 3D Engine (O3DE) is an Apache 2.0-licensed multi-platform 3D
Embeddable unity game engine view for Flutter
Game engine supporting many 3D/2D formats and graphic effects
GemRB is a portable open-source implementation of the Infinity Engine
A modern, cross-platform Quake game engine based on FitzQuake.
Vivid3D is an open-source 3D engine with powerful 2D UI.
3D Scene Builder
Vivid is a modern C++ 3D engine using OpenGL4+
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
Go 3D Game Engine
DOOM / Heretic / Hexen source port with enhanced graphics and UI
Data-oriented and data-driven game engine written in Rust
3D Game engine with editor
3D playground built on three.js and cannon.js
Cross-platform 2D and 3D game engine