Ballydesmond (Irish: Baile Deasumhan), formerly known as Kingwilliamstown, is a rural village in County Cork, Ireland. It is alongside the Blackwater River (near its source in Menganine) on the Cork-Kerry border. The village centre is located on the R577 regional road where it is joined by the R578 from the north and just west of where it is joined by the R582 from the south, and is about 45 kilometres west of Mallow, 17 kilometres west of Newmarket and 20 kilometres east of Castleisland, County Kerry. The Ballydesmond quarry is an area of geological interest, containing the best example of tundra forest polygons found in Ireland.