Isabel de Beaumont, Duchess of Lancaster, of theHouse of Brienne (c. 1318 – 1361) was an English-French noblewoman. She was the youngest daughter and child ofHenry de Beaumont, Earl of Buchan andAlice Comyn, Countess of Buchan.^[1]

Isabel was born in about 1318. She had nine siblings,^[1] including John de Beaumont, 2nd Lord Beaumont. Isabel's paternal grandparents wereLouis of Brienne, Viscount de Beaumont, and Agnes, Viscountess de Beaumont.^[1] Her maternal grandparents wereAlexander Comyn, Sheriff of Aberdeen and Joan le Latimer.^[1] Louis of Brienne was a younger son ofJohn of Brienne by his third wife,Berengaria of Leon while Alexander Comyn was a younger brother ofJohn Comyn, Earl of Buchan.

She marriedHenry of Grosmont, 1st Duke of Lancaster in 1330, but lived apart from her husband for a few years before consummation of the marriage due to her age.^[1] As her husband's mother had died before the marriage, she became the senior lady of the Lancaster household.^[1]

Isabel accompanied her husband on some of his diplomatic travels to the continent, such as to theLow Countries in 1341 andGascony in 1345.^[2] In 1351, he was awarded the title Duke of Lancaster and Isabel became Duchess of Lancaster, the first woman in England to hold the title.^[1]

Isabel and Henry had daughters who would eventually inherit their father's estates:

• Maud, Countess of Leicester (4 April 1339 – 10 April 1362), married firstly to Ralph Stafford, son ofRalph Stafford, 1st Earl of Stafford, whilst still a child, and married secondly toWilliam V, Count of Hainaut.^[3] Died without surviving issue.
• Blanche, Countess of Lancaster^[4] (25 March 1345 – 12 September 1368), marriedJohn of Gaunt, the third surviving son of KingEdward III of England andPhilippa of Hainault,^[5] by whom she had seven children, with three surviving to adulthood. Blanche inherited all her father's estates after the death of her sister.

Isabel may have been a godmother ofIsabella, Countess of Bedford, Edward and Philippa's second child.^[1]

Isabel died of theplague in 1361 atLeicester Castle. She was buried in Newark Abbey, Leicester. Her husband also died of the plague in March 1361.

With her husband, Isabel founded the College of the Annunciation of St Mary in Newark, Leicester.^[1]

Through Blanche, Isabel was an ancestress of England’s RoyalHouse of Lancaster, withHenry IV of England being her grandson.Philippa of Lancaster, Queen of Portugal andElizabeth of Lancaster, Duchess of Exeter were also her grandchildren.^[6]

• Daughters of Scottish earls
• English duchesses by marriage
• House of Brienne
• 1361 deaths
• 14th-century deaths from plague (disease)
• 14th-century English nobility
• 14th-century English women

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