Michael Charles "Mike" Costin (born 10 July 1929, in Hendon) was, together with Keith Duckworth, the co-founder of Cosworth Engineering, a producer of Ford-funded and sponsored engines. Drivers including Jackie Stewart, Emerson Fittipaldi and Nelson Piquet won the Formula One World Championship using Cosworth DFV engines during the 1970s.
He was educated at Salvatorian College in Wealdstone and then apprenticed at De Havilland. In 1953 he started at Lotus, initially helping out on a part-time basis. Keith Duckworth joined Lotus in 1957 and they founded Cosworth Engineering in 1958. He later described himself as having "studied for 40 years at the University of Duckworth".
In recent years he has been a consultant to the revived Triumph motorbike company.
Mike Costin is the younger brother of Frank Costin, an aerodynamics and race car designer for Lotus, Lister and Maserati, and co-founder of Marcos Cars.