Thomas Despenser, 2nd Baron Despenser, 1st Earl of Gloucester KG (22 September 1373 – 13 January 1400) was the son of Edward le Despenser, 1st Baron le Despencer, whom he succeeded in 1375.

A supporter of King Richard II against Thomas of Woodstock and the Lords Appellant, Despenser was rewarded with an earldom as Earl of Gloucester in 1397, by virtue of being descended from Gilbert de Clare, 7th earl of an earlier creation.^[1] He spent the years 1397–99 in Ireland, attempting with little success to persuade the Gaelic chieftains to accept Richard II as their overlord.

However, Despenser supported Henry Bolingbroke on his return to England to become King Henry IV, only to be attainted (deprived of his earldom because of a capital crime) for his role in the death of Thomas of Woodstock.

Despenser then took part in the Epiphany Rising, a rebellion led by a number of barons aimed at restoring Richard to the throne by assassinating King Henry IV; this quickly failed when the conspirators were betrayed by Edward of Norwich, 2nd Duke of York to Henry. After fleeing to the western counties, a number of the Epiphany Rising conspirators were captured and killed by mobs of townspeople loyal to the king; Despenser was captured by a mob and beheaded at Bristol on 13 January 1400.^[1]

Thomas Despenser married Constance, daughter of Edmund of Langley, 1st Duke of York and Isabella of Castile, Duchess of York. They had issue:

• Elizabeth Despenser (died young c. 1398)
• Richard Despenser, 4th Baron Burghersh (1396–1414)
• Edward Despenser (born before 1400), died young
• Hugh Despenser (c. 1400 – 1401)
• Isabel Despenser (26 July 1400 – 27 December 1439); she married, firstly, Richard Beauchamp, 1st Earl of Worcester, and later married, secondly, his cousin Richard de Beauchamp, 13th Earl of Warwick.