Progress Rail Locomotives, doing business as Electro-Motive Diesel (EMD) is an American manufacturer of diesel-electric locomotives, locomotive products and diesel engines for the rail industry. The company is owned by Caterpillar through its subsidiary Progress Rail.

Electro-Motive Diesel traces its roots to the Electro-Motive Engineering Corporation, a designer and marketer of gasoline-electric self-propelled rail cars founded in 1922 and later renamed Electro-Motive Company (EMC). In 1930, General Motors purchased Electro-Motive Company and the Winton Engine Co., and in 1941 it expanded EMC's realm to locomotive engine manufacturing as Electro-Motive Division (EMD).

In 2005, GM sold EMD to Greenbriar Equity Group and Berkshire Partners, which formed Electro-Motive Diesel to facilitate the purchase. In 2010, Progress Rail completed the purchase of Electro-Motive Diesel from Greenbriar, Berkshire, and others.

EMD's headquarters, engineering facilities and parts manufacturing operations are based in McCook, Illinois, while its final locomotive assembly line is located in Muncie, Indiana. EMD also operates a traction motor maintenance, rebuild and overhaul facility in San Luis Potosí, Mexico.

As of 2008, EMD employed approximately 3,260 people, and in 2010 it held approximately 30 percent of the market for diesel-electric locomotives in North America.