Margaret Holland, Countess of Somerset (1385 – 31 December 1439) was the daughter of Thomas Holland, 2nd Earl of Kent, who was the son of Joan "the Fair Maid of Kent" (granddaughter of Edward I of England, wife of Edward the Black Prince and mother of Richard II of England). Margaret's mother was Alice FitzAlan, daughter of Richard FitzAlan, 10th Earl of Arundel and Eleanor of Lancaster.

Margaret married John Beaufort, 1st Earl of Somerset, son of John of Gaunt, 1st Duke of Lancaster' and his mistress Katherine Swynford. They had six children:

• Henry Beaufort, 2nd Earl of Somerset (c. 1401–25 November 1418).
• John Beaufort, 1st Duke of Somerset (baptized 25 March 1404–27 May 1444).
• Thomas Beaufort, Count of Perche (c. 1405–1431).
• Lady Joan Beaufort (c. 1406–15 July 1445), who married James I of Scotland and Sir James Stewart, the Black Knight of Lorn.
• Edmund Beaufort, 2nd Duke of Somerset (c. 1406–22 May 1455).
• Lady Margaret Beaufort, Countess of Devon (c. 1409–1449), married Thomas de Courtenay, 13th Earl of Devon.

In 1399, she was invested as a Lady Companion, Order of the Garter (L.G.). After Beaufort died in 1410 (in the Tower of London), she married his nephew Thomas of Lancaster, 1st Duke of Clarence, the son of King Henry IV. They had no children. She died on 31 December 1439 at St. Saviour's Abbey, Bermondsey, in London, England. Margaret and both her husbands are buried together in a carved alabaster tomb in Canterbury Cathedral that shows her lying between the two of them.

Descendants

Through her son, the 1st Duke of Somerset, Lady Margaret is an ancestress to the Tudor monarchs. Both Lady Joan, Queen consort of Scotland, and the Duke of Somerset, are ancestors of King George I of Great Britain. As such, both children are ancestors to the current British royal family.