Thomas FitzWilliam, 1st Viscount FitzWilliam

Thomas FitzWilliam, 1st Viscount Fitzwilliam (1581–1650) was an Irish nobleman of the Stuart age. He was born to wealth and privilege, and acquired a peerage, but due to his loyalty to the English Crown his estates suffered greatly during the English Civil War, and he died in poverty.

He was born in Dublin, probably at Merrion Castle, eldest of the five sons of Sir Richard FitzWiliam, Constable of Wicklow, and Jane Preston, daughter of Christopher Preston, 4th Viscount Gormanston. The FitzWilliam family are recorded in Dublin from about 1210, and by the time of Thomas's birth they were among the wealthiest and most influential families in the Pale.

Thomas was only fourteen when his father died. As a young man he spent some time in London studying law at Gray's Inn. He was knighted in 1605, the year of his marriage.

In 1608 he narrowly avoided entanglement in the rebellion of Sir Cahir O'Doherty, having stood surety for the good behaviour of O'Doherty, who had married Tomas's aunt Mary Preston. A messenger arrived at Merrion Castle ordering FitzWilliam to produce the person of O'Doherty; fortunately FitzWilliam was not at home. No doubts seem to have been entertained about his own loyalty to the Crown, except perhaps during the latter part of the English Civil War, and in 1629 King Charles I created him Viscount FitzWilliam in recognition of his family's long record of service to the Crown. It appears that a good deal was expected in return for the title, and Thomas had to make substantial gifts to the Crown. This put a particular burden on his estates since he was involved in protracted litigation with his numerous brothers and sisters, due to his father's breaking of an entail on the estates, which benefitted Thomas but not his siblings. Like nearly all of his family he inclined to the Roman Catholic faith, while adhering in public to the Church of Ireland; later generations of Fitzwilliams were more overt in their support for the Catholic religion.

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