Philippa of Clarence was the suo jure Countess of Ulster.
Background
She was born at Eltham Palace in Kent on 16 August 1355, the only child of Lionel of Antwerp, 1st Duke of Clarence, and Elizabeth de Burgh, 4th Countess of Ulster. Her father was the third son, but second son to survive infancy, of King Edward III of England and Philippa of Hainault.
Career
Philippa married Edmund Mortimer, 3rd Earl of March, in 1368 at the age of twelve in the Queen"s Chapel at Reading Abbey, an alliance that would have far-reaching consequences in English history. He was killed in a skirmish at Kells, County Meath, in Ireland in 1398, making his six-year-old son, Edmund Mortimer, 5th Earl of March, Richard"s heir presumptive. Philippa died in 1378, and was buried at Wigmore Abbey, Herefordshire.