O.S. Engines is a Japanese model engine manufacturer.
The company was founded in 1936 by machinist Shigeo Ogawa for the production of model steam engines. At the suggestion of American buyer Paul Houghton, Ogawa tooled up for his first gasoline-powered engine, the 1.6 cc O.S. Type-1 of which 200 units were produced and exported under the brand name "Pixie."
Today, O.S. Engines produces a line of engines that includes the only Wankel rotary aircraft engine which was first introduced in 1970. O.S. is also a leading manufacturer of multi-cylinder aircraft engines which include the FF-320, a giant-scale flat four-cylinder and the FR5-300, a five-cylinder, giant-scale radial.