The Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij 18 Tonner 0-6-0ST of 1890 is a South African steam locomotive from the pre-Union era in the Transvaal.In 1890 the Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij of the Zuid-Afrikaansche Republiek (Transvaal Republic) placed six saddle-tank locomotives with a 0-6-0 wheel arrangement in service on construction work. Since the railway classified its locomotives according to their weight, these locomotives were known as the 18 Tonners.