The Blackstaff River is a watercourse that flows underneath the city of Belfast, Northern Ireland. It was formerly an overground river, but much of it was culverted and built over in the late 19th century. It rises on the slopes of Black Mountain and enters the River Lagan a short distance east of Belfast city centre. It was historically known as the Owenvarra, which comes from Irish Abhainn Bheara, meaning "river of the staffs".