The E9 is a 2,400-horsepower (1,790 kW), A1A-A1A passenger train-hauling diesel locomotive built by General Motors' Electro-Motive Division of La Grange, Illinois, between April 1954 and January 1964. 100 cab-equipped A units were produced and 44 cabless booster B units, all for service in the United States. The E9 was the tenth and last model of EMD E-unit and differed from the earlier E8 as built only by the newer engines and a different, flusher-fitting mounting for the headlight glass, the latter being the only visible difference. Since some E8s were fitted with this, it is not a reliable way to distinguish the two. The E9 has two 1,200 hp (895 kW), V12 model 567C engines, each engine driving one generator to power two traction motors.

Electro-Motive Diesel is a brand of diesel-electric locomotives, locomotive products and diesel engines for the rail industry. Formerly a division of General Motors, EMD has been owned by Progress Rail since 2010. Electro-Motive Diesel traces its roots to the Electro-Motive Engineering Corporation, founded in 1922 and purchased by General Motors in 1930. After purchase by GM, the company was known as GM's Electro-Motive Division. In 2005, GM sold EMD to Greenbriar Equity Group and Berkshire Partners, and in 2010, EMD was sold to Progress Rail. Upon the 2005 sale, the company was renamed to Electro-Motive Diesel.