The NSB type 15 was a 2-6-0 locomotive designed as a successor for the type 11. Between 1896 and 1902, 16 locomotives of the types 15a, 15b and 15c were built by different manufacturers from Scotland, Germany and Norway. They had a two-cylinder compound engine and compared to their predecessors, they had a larger three-axle tender. Designed as freight locomotives, they were also used for slow passenger trains.

Although only a small number was built, they ultimately made it to a total number of eight variants through the rebuilding of the original types 15a, 15b and 15c. By superheating them, the variants d and e were created. The variants f, g and h were created by superheating and simpling them. Three locomotives of type 11 were even rebuilt to type 15. Nevertheless, seven locomotives of type 15c remained in their original state and were withdrawn between 1935 and 1950. The last 15f was withdrawn in 1956.