Philippa Plantagenet, 5th Countess of Ulster was born 16 August 1355 in Eltham Palace, Kent, England, United Kingdom to Lionel of Antwerp, 1st Duke of Clarence (1338-1368) and Elizabeth de Burgh, 4th Countess of Ulster (1332-1363) and died 5 January 1382 County Cork, Ireland of unspecified causes. She married Edmund Mortimer, 3rd Earl of March (c1352-1381) 1368 JL .
Philippa Plantagenet, 5th Countess of Ulster, (August 16, 1355 – January 5, 1382), Countess of Ulster suo jure.
Philippa was born in Eltham Palace, Kent, England on August 16, 1355. She was the daughter and only child of Lionel of Antwerp, 1st Duke of Clarence, and Elizabeth de Burgh, 4th Countess of Ulster. Her father was the second son of King Edward III of England by his Queen consort, Philippa of Hainault.
Philippa married Edmund Mortimer, 3rd Earl of March (1351? – December 27, 1381) in about 1368, at Reading Abbey, an alliance that would have far-reaching consequences in English history. As a result of her seniority in the line of succession to the throne of the Kingdom of England and her marriage into the powerful Mortimer family, her descendants eventually succeeded to the throne as the House of York under Edward IV.
She died on January 5, 1382 in Cork, Ireland, and was buried in Wigmore, Herefordshire.
Children
| Name | Birth | Death | Joined with |
| Elizabeth Mortimer (1371-1417) | February 1371 Usk, Monmouthshire, Wales, United Kingdom | 20 April 1417 | Henry Percy (c1363-1403) Thomas de Camoys, 1st Baron Camoys (c1351-1421) |
| Roger Mortimer, 4th Earl of March (1374-1398) | 11 April 1374 Usk, Monmouthshire, Wales, United Kingdom | 20 July 1398 Kells, County Meath, Ireland | Alianore Holland (c1373-1405) |
| Philippa Mortimer (1375-1400) | 21 November 1375 Ludlow Castle, Ludlow, Shropshire, England, United Kingdom | 26 September 1400 Halnaker, Sussex, England, United Kingdom | John Hastings, 3rd Earl of Pembroke (1372-1389) Richard FitzAlan, 11th Earl of Arundel (1346-1397) Thomas Poynings, 5th Baron St John (-1429) |
| Edmund Mortimer (1376-1409) | |||
Footnotes (including sources)
| ‡ General |