Game engine developed by Epic Games, Inc. for their hit 1998 Action game Unreal and later members of the Unreal Series.
Versions of the Unreal engine have been licensed for use (often heavily modified) in many games including Star Trek Klingon Honor Guard, Wheel of Time, Rune, Duke Nukem Forever, Clive Barker's Undying, Infiltration, TNN Outdoors Pro Hunter and Dr Brain: The Ultimate Games For your Brain and X-COM: Alliance.
Epic also license the Unreal Tournament Engine treated separately here.
Information is available on the Epic corporate Website epicgames.com.
In May 2000, Rage Software, the UK-based publisher and developer, entered an agreement with Epic giving it the exclusive right to sublicense the engine in Europe.