Free / Open Source Engines

> Axiom Engine - Fork containing the core of the OGRE graphics engine written in C#.
> Boom - Port of the Doom source code by TeamTNT.
> bo3d - BlitzMax wrapper for Ogre3D engine.
> BlendELF - OpenGL Lua/C++ 3D game engine.
> Build engine - First-person shooter engine used to power Duke Nukem 3D.
> Cadabra 3D - Brazilian LGPL 3D game engine.
> Cat Mother - BSD-licensed engine from a company that open-sourced its code when it closed the business.
> Crystal Entity Layer - Extension of the Crystal Space 3D Engine.
> Crystal Space - General framework for developing 3D applications.
> Cube - Powers the computer game of the same name.
> DarkPlaces - One of the most advanced free software Quake engines.
> Daybreak motor - Flexible, object-oriented graphics rendering engine for .NET and XNA (XNA 3D Engine).
> Delta3d - Integrates other well-known free software projects into an easy-to-use API. Developed by the U.S. Navy.
> dim3 - Free 3D javascript engine for the Mac (although finished games are cross platform).
> Doom engine - The now free software engine originally used for the hugely popular Doom and Doom II.
> DXFramework - Simple, pedagogical 2D/3D DirectX-based game engine for Visual Studio.
> Flatredball - 2.5D game engine written in C# with XNA and MDX.
> G3D - Commercial-grade C++ 3D engine available as Open Source (BSD License).
> Game Blender - Flexible, node-based game logic engine Blender 3D.
> Genesis3D - Real-time 3D engine for Windows.
> Genesis Device - Powerful FPS engine using OpenGL (LGPL).
> Horde3D - Lightweight next-generation graphics engine.
> id Tech 2 - Formerly known as the "Quake II engine", open-sourced engine from id Software.
> id Tech 3 - Formerly known as the "Quake III engine", derived from id Tech 2 (GPL).
> ioquake3 - Cleaned-up, bugfixed and updated fork of the original id Tech 3 engine.
> IrrLicht Engine - Cross-platform and lightweight 3D graphics engine.
> KjAPI - C++ technology to create games and 3D applications for PC computers.
> Luxinia - 3D OpenGL engine written in C.
> Medusa (engine) - C++ 3D game engine developed by Palestar and used in the DarkSpace MMO.
> MiniB3D - Open-source OpenGL engine written in BlitzMax, designed as a cross platform version of Blitz3D.
> jMonkeyEngine - Open-source, BSD licensed Java scenegraph engine.
> Lightfeather 3D Engine - Cross-platform, zlib licensed, real-time 3D graphics engine.
> Nebula Device - Realtime 3D game engine developed by German game studio Radon Labs.
> N3xtD - Successor to Dreamotion 3D, based on the IrrLicht Engine.
> Ninfa3D - A combination of Irrlicht, OpenAL and Newton.
> OGRE Engine - Very popular object-oriented graphics rendering engine. Also called OGRE3D.
> Panda3D - Relatively easy to use python-driven game engine by Disney.
> PhyreEngine - Cross-platform (PC & PS3) graphics engine from Sony Computer Entertainment.
> PLIB - 3D Game engine featuring Audio, Music, GUI, Window manager and is portable Linux/Windows/Mac OS X.
> PySoy - Multi-threaded 3d game engine for Python, freely licensed under the GPLv3 for Linux, Mac OS X, and Windows.
> RealmForge - Open-source game engine for the Microsoft .NET Framework, predecessor to Visual3D.NET.
> Retribution Engine - Game engine to make first person shooter games.
> Sauerbraten - Upgraded engine forked from the Cube engine.
> Sith (engine) - Game engine developed by LucasArts for Jedi Knight: Dark Forces II.
> Soya 3D - Object oriented "high level" 3D engine for Python.
> Sylphis3D - Game engine with unified lighting and shadowing, physics and fully python scripted (GPL v2).
> Yake - Small, flexible, cross-platform game engine / application framework.

Commercial Engines

> 3Impact - Middleware, game developing system for Windows Vista/XP.
> A7 - The engine behind the Gamestudio authoring system.
> C4 Engine - Emerging next-generation computer game engine created by Eric Lengyel.
> Cipher - game engine offering everything from fast graphics rendering to support for compressed pak files.
> ColdSteel - Based on the IrrLicht engine. Features include game content editors and support for AngelScript.
> DX Studio - Engine and editing suite that allows rapid creation of real-time games and simulations.
> Esenthel Engine - Full-featured DirectX-only game engine.
> Esperient Creator - 3D visualization and media software tools. Formerly called Deep Creator.
> Euphoria - Real-time motion synthesis engine by NaturalMotion.
> Flow3D - BlitzMax engine based on OGRE featuring Newton physics and a scriptable GUI system.
> Leadwerks Engine - OpenGL-based game engine featuring a unified lighting system with dynamic soft shadows.
> NeoAxis Engine - Game engine and toolkit designed for 3D simulations, visualizations and games.
> Power Render - General purpose software development kit for games and 3D visualization.
> Quest3D - Development tool for creating real-time applications such as architecture demos and training simulators.
> Realm Crafter - 3D MMORPG specific game engine with an easy click-and-drop design. Easy to learn scripting language.
> Revolution3D - 3D graphics engine developed by X-Dream Project.
> ShiVa - All-in-one 3D real-time development platform, based on the cross-platform Ston3D engine.
> Torque Game Engine - 3D engine originally developed by Dynamix for Tribes 2.
> Torque Game Engine Advanced - Rewrite of TGE to provide massive terrains, shaders and per-pixel lighting.
> Truevision3d - 3D game engine using the DirectX API.
> Unity (game engine) - Easy-to-use cross-platform 3D engine for games or other interactive software.
> Visual3D.NET - 3D platform and visual development environment built upon Microsoft .NET 2.0 and XNA Framework.
> Xors3D - Advanced DirectX 9 game engine.