The 18th AAF Base Unit (Motion Picture Unit), originally known as the First Motion Picture Unit, Army Air Forces, was the primary film production unit of the U.S. Army Air Forces (AAF) during World War II, and was the first military unit made up entirely of professionals from the film industry. It produced more than 400 propaganda and training films, which were notable for being informative as well as entertaining. Films for which the unit is known include Resisting Enemy Interrogation, Memphis Belle: A Story of a Flying Fortress and The Last Bomb—all of which were released in theatres. Veteran actors such as Clark Gable, William Holden, Clayton Moore, Ronald Reagan, Craig Stevens and DeForest Kelley, and directors such as John Sturges served with the 18th AAF Base Unit. The unit also produced training films and trained combat cameramen.

First Motion Picture Unit is also the eponymous title of a 1943 self-produced documentary about the unit narrated by radio and television announcer Ken Carpenter.