SM91 is the Norwegian designation for a tram type which operated on the Oslo Tramway until 2002. The trams were imported from Sweden, where they had originally run on the Gothenburg Tramway under the designation M25. The trams were originally delivered to the Gothenburg Tramway between 1958 and 1961. A total of 36 trams were eventually exported to Oslo, Norway, numbered 264 to 299.