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". It is likely that this referred to a crossing made from oak beams, and that the "black" element referred to the colour of the beams.
The Blackstaff is known as a "Designated Watercourse" and is controlled and maintained by the Department of Agriculture and Rural Development's Rivers Agency. It has been cited as a main contributor to the high flood risk in central and low-lying areas of Belfast. In particular on 16 August 2008, a newly opened underpass carrying the M1 motorway onto the A12 Westlink controversially flooded to a depth of 20 feet (6.1 m) during heavy rain with water from the culverted Blackstaff and Clowney Rivers.
- PlaceNames NI: Blackstaff River
- "Locations at significant risk (Greater Belfast Sub Plan)". Greater Belfast pilot study. Rivers Agency. Retrieved 21 August 2012.
- "Widespread chaos caused by floods". bbc.co.uk/news. BBC News Online. 16 August 2008. Retrieved 21 August 2012.
- Broadway Underpass – Westlink, Belfast:Independent Report into the Flooding Incident on 16 August 2008 (PDF) (Report). Amey Consulting. October 2008. Retrieved 21 August 2012.
- Rivers Agency of Northern Ireland.