The Douglas O-38 was a United States Army Air Corps observation aircraft of the 1930s. It was a single-engine, open cockpit biplane with fixed landing gear. The O-38 was used for reconnaissance, artillery spotting, and other roles that required a relatively slow-flying aircraft with good visibility. It was powered by a single Pratt & Whitney R-1690 Hornet radial engine and had a maximum speed of around 120 mph. The O-38 was used by the Army Air Corps from the mid-1930s until the early 1940s, when it was replaced by more modern aircraft.