The SD45 is a six-axle diesel-electric locomotive class built by General Motors Electro-Motive Division between 1965 and 1971. It has an EMD 645E3 twenty-cylinder engine generating 3,600 hp (2,680 kW) on the same frame as the SD38, SD39, SD40, and SDP40. As of 2023, most SD45s have been retired, scrapped or rebuilt to SD40-2 standards.

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.