Godot is a powerful cross-platform game engine
Open source voxel game engine with support for survival and crafting
Xash3D FWGS engine
scene-oriented, flexible 3D engine (C++, Python, C#, Java)
The game engine for everyone
Voxel game-creation platform with easy modding and game creation
Multi-platform 2D and 3D game engine
Cocos simplifies game creation and distribution with Cocos Creator
Free, cross-platform 2D game engine powered by Haxe and OpenFL
Open source library for creative expression on the web, desktop, etc.
Multi-platform Engine for Desktop, XBOX (UWP) and Mobile games
A dead simple 2D game engine for Go
New Godot bindings for Swift
Cross-platform game engine in Rust
GemRB is a portable open-source implementation of the Infinity Engine
A complete 2D/3D Arcade Game Engine for Browser (Blender compatible)
Cross-platform 2D game engine (+ full OpenGL, +full OpenGL ES )
Orx: Portable Game Engine
Urho3D Game engine
Game engine to build text adventures.
Open source reimplementation of GTA San Andreas game engine in Unity
Cross-platform 2D and 3D game engine
Real-time RPG for PC/tablet/phone; multiple quests and random dungeons
Multi-threaded game engine for Android