Sir William Óg de Burgh (; ; died 1270) was an Anglo-Irish noble and soldier who was the ancestor of the Earls of Clanricarde and the Mac William Iochtar (Burkes of County Mayo). Career William Óg was the third son of Richard Mor de Burgh, Lord of Connacht. He served with distinction in France with King Henry III (1245) and later in Scotland. He was involved in fierce feudal warfare in Ireland where he killed the Lord of Desmond. He was killed at the Battle of Áth an Chip or Athankip by the Ua Conchobair Kings of Connacht, in 1270. Family He was survived by at least one son, Sir William Liath de Burgh (d.1324), Custos or Warden of Ireland (who married Una, a daughter of the Mac Jordan of Connacht). William Óg was the ancestor of the Burke (de Burgh) Earls of Clanricarde and the Mac William Iochtar (Burkes of County Mayo). Genealogy Walter de Burgh of Burgh Castle, Norfolk m. Alice William de Burgh (d. 1206) m. Daughter of Domnall Mór Ó Briain, King of Thomond Richard Mór / Óge de Burgh, 1st Lord of Connaught m. Egidia de Lacy, Lady of Connacht Sir Richard de Burgh (d.1248), 2nd Lord of Connaught Walter de Burgh, 1st Earl of Ulster (d. 1271) Richard Óg de Burgh, 2nd Earl of Ulster (1259–1326) John de Burgh m. Elizabeth de Clare William Donn de Burgh, 3rd Earl of Ulster (1312–33) m. Maud of Lancaster Elizabeth de Burgh, 4th Countess of Ulster (1332–63) m. Lionel of Antwerp, 1st Duke of Clarence Philippa Plantagenet, 5th Countess of Ulster (1355–82) m. Edmund Mortimer, 3rd Earl of March Roger Mortimer, 4th Earl of March, 6th Earl of Ulster (1374–98) Edmund Mortimer, 5th Earl of March, 7th Earl of Ulster (1391–1425) Anne Mortimer (1388–1411) m. Richard of Conisburgh, 3rd Earl of Cambridge Richard of York, 3rd Duke of York, 8th Earl of Ulster (1411–60) Edward IV (Edward, 4th Duke of York, 9th Earl of Ulster) House of York (Kings and Queens of England and Ireland) Edmond de Burgh Sir Richard Burke Walter Burke (d. 1432) Burkes of Castleconnell and Brittas (Clanwilliam) Uileag Carragh Burke Burkes of Cois tSiúire (Clanwilliam) Sir David Burke, Burkes of Muskerryquirk (Clanwilliam) Elizabeth, Queen of Scotland m. Robert I of Scotland Theobald de Burgh William de Burgh Thomas de Burgh Egidia de Burgh William Óg de Burgh (d. 1270) William Liath de Burgh