The SNCB Class 55 is a series of 42 diesel locomotives ordered by the SNCB in the early 1960s. It forms, with the series 51, the backbone of the second generation Belgic DMU trains (the first consisting of series 52, 53 and 54). In the old numbering system used by the SNCB, the series 55 is known as type 205. The 55 series locomotives were commissioned between 1961 and 1962 in a dark green and yellow livery. Like those of series 52 and 53, the Class 55 is equipped with an engine designed by General Motors.