Open-source engine for Heroes of Might and Magic III
Magic Another Game Engine
DOOM / Heretic / Hexen source port with enhanced graphics and UI
Fast and lightweight JavaScript game engine built on WebGL and glTF
Free game engine for development of desktop, mobile, and web games
fheroes2 is a recreation of Heroes of Might and Magic II game engine
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
Open 3D Engine (O3DE) is an Apache 2.0-licensed multi-platform 3D
Cross-platform 2D and 3D game engine with modular architecture
A refreshingly simple data-driven game engine built in Rust
An open source re-implementation of Diablo 2
A modular Common Lisp game engine
Free, open source game engine online
Amazon Lumberyard is a free AAA game engine
Blueshift is a cross-platform 3D game engine implemented in C++
The flexible game engine
2D game development library for Ruby and C++
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
Descent 3 by Outrage Entertainment
Cross-Platform C++ 2D/3D game engine
The ioquake3 community effort to continue supporting/developing id's
The multiplayer game engine
JavaScript-based game engine designed to empower developers
The Open Toolkit library is a fast, low-level C# wrapper for OpenGL
3D playground built on three.js and cannon.js