Ballydesmond (Irish: Baile Deasumhan), formerly Kingwilliamstown, is a rural village in County Cork, Republic of Ireland. It is alongside the Blackwater River (near its source in Menganine) on the Cork-Kerry border. The Ballydesmond quarry is an area of geological interest, containing the best example of tundra forest polygons found in Ireland.
Ballydesmond was established in the 1830s as a model village, and named Kingwilliamstown after King William IV of the United Kingdom. It had formerly been known as Tooreenkeogh. In 1951, it was officially renamed Ballydesmond, an anglicisation of the Irish name Baile Deasumhan. This is thought to refer to legendary freedom fighter, the 15th Earl of Desmond, who is believed to have taken refuge in the nearby hills. However, Kingwilliamstown remained the official name of the townland.
Daniel Buckley and Bridget Delia Bradley from Ballydesmond survived the sinking of the RMS Titanic.
The Tureengarriffe ambush occurred near Ballydesmond, where a number of British army officers were killed during the Irish War of Independence by untrained members of the local flying column of the Irish Republican Army. Nora Herlihy, a founder member of the Irish League of Credit Unions, is from Ballydesmond.