BUILD is a 3D engine written by young programmer Ken Silverman. It is best known for powering such well-known games as 3D Realms' Duke Nukem 3D and Shadow Warrior, and less known for having been licensed to such projects as Exhumed and TekWar.

Although most people don't recognize it, Build first made its appearance as an engine based on id's Wolfenstein game. The game was called Ken's Labyrinth, and was released independently as shareware.

3D Realms noticed the young programmer and hired him to write the engine for what was then to be the sequel to Wolfenstein 3D, but ended up being the game Rise of the Triad.

As a 3D level builder, it is best known for being extremely easy to use, and yet advanced for its time. Most of the actual mapping took place in a visual environment, where you could literally walk around in your level while it was being built. You could walk up to a wall and go, "This wall should have a different texture", point to the wall, hit a few quick keystrokes, and WHAM - the wall changed texture before your very eyes. And yet, you could have moving subway cars, rotating sectors, teleporters, Star Trek doors, a very limited rooms-above-rooms system, and other advanced techniques too.

Build has now been retired, since it was not completely 3D (most 3D elements were accomplished by flattening sprites and having them levitate in the air, creating the illusion of a bridge or catwalk) and most 3D gamers these days aren't too fond of sprite enemies.