John of Gaunt (1340–1399)

English noble and politician, fourth (and third surviving) son of Edward III, Duke of Lancaster from 1362. He distinguished himself during the Hundred Years' War. During Edward's last years, and the years before Richard II attained the age of majority, he acted as head of government, and Parliament protested against his corrupt rule.

He was called John of Gaunt because he was born in Ghent, Flanders. In 1359 he married Blanche, daughter of Henry, Duke of Lancaster (died 1361), whose title passed to John of Gaunt in 1362; their son became Henry IV of England. Blanche died in 1369 and three years later he married Constance, daughter of Pedro III of Castile. Their daughter Philippa (1359–1415) married King John I of Portugal (1357–1433). John of Gaunt assumed the title of King of Castile in 1372, but his efforts to establish his claim against his rival, Henry of Trastamare, proved unsuccessful; in 1387 he renounced all claims in favour of his daughter Catherine, who married Henry III of Castile (1379–1406) in 1393.

Constance died in 1394, and John of Gaunt married his mistress of long standing, Katharine Swynford (c. 1350–1403), with whom he already had four children; they were legitimized in 1397 by charter of Richard II, and founded the house of Beaufort, from whom Henry VII was descended.