Mary was born circa 1368 as the daughter of Humphrey de Bohun, 7th Earl of Hereford and Joan Fitzalan. She and her older sister Eleanor were heiresses to her father’s estates, as they had no brothers. Eleanor was married off to Edward III’s son Thomas of Woodstock who intended to keep the entire inheritance for herself by forcing Mary to become a nun. She was abducted from the convent by her future father-in-law John of Gaunt, a brother of Thomas of Woodstock. She was married to his son Henry, the future Henry IV on 27 July 1380 at Arundel Castle. She was just 12 years old. Though they were under instruction not to consummate the marriage too soon, they disobeyed, and Mary became pregnant at the age of 14. She gave birth to a son who lived for only a few days.
Besides the short-lived son, she and Henry had six children.
Her children were:
- Henry V, King of England (1386–1422)
- Thomas of Lancaster, 1st Duke of Clarence (1387–1421)
- John of Lancaster, 1st Duke of Bedford (1389–1435)
- Humphrey, Duke of Gloucester (1390–1447)
- Blanche of England (1392–1409) married in 1402 Louis III, Elector Palatine.
- Philippa of England (1394–1430) married in 1406 Eric of Pomerania, King of Denmark, Norway and Sweden.
Mary died in childbirth with her last child, Philippa, still only 28 and she never lived to see her husband become King. Her son became King following his father, but he died young, leaving an infant son.