Oliver FitzWilliam, 1st Earl of Tyrconnell (died 11 April 1667) was an Irish nobleman.
His father was Thomas FitzWilliam, 1st Viscount FitzWilliam, who was born in 1581 and died 1665.
He was both a Catholic and a royalist. In 1645 he tried to get the Confederation of Kilkenny to support King Charles I in the English Civil War on the grounds that their Catholic demands would be met. He fought with the Confederates against the Parliamentarians in 1645–6, and led a successful assault on Roscommon Castle in 1646.
He died at Merrion Castle, 11 April 1667, and was buried on 12 April 1667 in Fitzwilliam Chapel, Donnybrook church.
1st marriage to Dorothy Brereton, 2nd marriage to Lady Eleanor Holles, daughter of John Holles, 1st Earl of Clare
| Peerage of Ireland | ||
|---|---|---|
| Preceded by Thomas FitzWilliam |
Viscount FitzWilliam 1650–1667 |
Succeeded by William FitzWilliam |
| New creation | Earl of Tyrconnell 1661–1667 |
Extinct |