John Beaufort, 1st Earl of Somerset, French-English admiral and politician, Lord Warden of the Cinque Ports (b. 1373)
John Beaufort, 1st Marquess of Somerset and 1st Marquess of Dorset, later only 1st Earl of Somerset, (c. 1373 – 16 March 1410) was an English nobleman and politician. He was the first of the four illegitimate children of John of Gaunt (1340–1399) (third surviving son of King Edward III) by his mistress Katherine Swynford, whom he later married in 1396.

The Beaufort children were declared legitimate twice by parliament during the reign of King Richard II of England, in 1390 and 1397, as well as by Pope Boniface IX in September 1396. Even though they were the grandchildren of Edward III and next in the line of succession after their father's legitimate children by his first two wives, the Beauforts were barred from succession to the throne by their half-brother Henry IV.