Oberhausen (ōˈbərhouˌzən) [key], city (1994 pop. 226,254), North Rhine–Westphalia, W Germany, a former industrial center of the Ruhr district. It is a port on the Rhine-Herne Canal and a rail junction. Chemicals are produced, and there are some light industries; coal mining and iron and steel production, once significant industries, came to an end in the 1990s. The first German steam engine was built in Sterkrade, now a district of Oberhausen, in 1814. Oberhausen was chartered in 1874. An aquarium is in the city.