The DF50 was a class of six-axle diesel-electric locomotives built for passenger and freight service. They were early members of a family of Bo-Bo-Bo locomotives built in Japan. Their designation stood for diesel (D), six powered axles (F) and a top speed above 85 km/h (50). To be precise, the maximum speed was 90 km/h. Depending on the need to haul passenger trains and the climate zone, some had steam generators and others did not. The weights given in the table are with steam generator and locomotives without were 3.9 tonnes lighter.

Two different variants were built basically at the same time. First, 65 locomotives of the series 0 were built by Kisha Seizō, Mitsubishi and Nippon Sharyō between 1957 and 1962. They had a 1,060 hp six-cylinder Sulzer and six 100 kW traction motors. The series 500 was built by Hitachi, Kawasaki and Toshiba between 1958 and 1963 and had a MAN V12 with 1,200 hp. Here, the traction motors had 110 kW each. They were retired by 1983 and three were preserved. But DF50 4 was damaged by a typhoon in 2018 and scrapped six years later.