James Fitzwilliam

James Fitzwilliam (died 1420) was an Irish landowner and judge who held the office of Chief Baron of the Irish Exchequer. He was the ancestor of the prominent Dublin landowning family which acquired the titles Viscount FitzWilliam and Earl of Tyrconnell.

He was the son of Hugh Fitzwilliam. The Fitzwilliam family are recorded in Dublin from about 1210. By the time of James' birth, they were already considerable landowners in Dublin, with their estates centred on Dundrum and Swords.

Few details of his legal career survive, but it is known that he was Chief Baron by 1413 and was superseded in 1417.

James died in 1420, and his lands passed to his son, Phillip, who was still a minor; the family estates are said to have suffered serious depredations during his minority. He was a ward of his father's successor as Chief Baron, James Cornwalsh;

Philip lived mainly at Thorncastle (his cousin Edward Cruys had died by 1432, although Edward did have a brother Christopher) which he rebuilt in 1437 after it was burnt in a raid by one of the Gaelic clans of County Wicklow. He received a grant from the English Crown for the necessary works, presumably because it was an important part of the city's defences. During the early stages of the Wars of the Roses, he was described as a "counsellor" to King Henry VI of England. Later he changed his allegiance and sided decisively with the House of York, giving good service against King Henry and his allies. Thorncastle passed to his son and heir Stephen, who was living there in 1463.