Gille Ruadh was the leader who led the revolt against King Alexander II of Scotland. His birth, death date and origins are all unknown, although it is strongly suspected that he was the leader of the MacDowell kindred.
Upon Alan, Lord of Galloway's death in 1234, Galloway was left without a legitimate feudal heir. Alexander II had decided to partition the lordship between the Anglo-Norman husbands of Alan's three living daughters, Roger de Quincy (married to Ela), John de Balliol (married to Derborgaill) and William de Forz (married to Cairistiona).
However, Alan had left an illegitimate son, Thomas. In Gaelic succession law, Thomas was a perfectly acceptable heir. Thus the native Galwegians and the Gaelic clergy of the province rose in revolt against the Scottish king.
The Revolt of the Galwegians started in 1235, under Gille Ruadh's leadership. Matthew Paris says that Manx and Irish forces got involved too. Thomas received help from his father's father-in-law, Hugh de Lacy the Earl of Ulster, Hugh had his own problems which limited his participation. Thomas also seems to have gained support from Ruaidrí mac Ragnaill of Garmoran and the Uí Domnaill of Tír Conaill.