thumb|Arms of FitzWilliam: [[Lozenge (heraldry)|Lozengy, argent and gules]]
Richard FitzWilliam, 5th Viscount FitzWilliam, PC (Ireland) (c. 1677 – 6 June 1743), of Mount Merrion in Dublin, was an Irish nobleman and Whig politician.
Origins
He was the only son of Thomas FitzWilliam, 4th Viscount FitzWilliam by his first wife Mary Stapleton, a daughter of the English statesman Sir Philip Stapleton and his first wife Frances Hotham. The FitzWilliam family is recorded in Ireland from about 1210, and by the seventeenth century had become one of the largest landowners in Dublin.
Career
He succeeded to the Viscountcy of FitzWilliam in 1704, and became a member of the Irish Privy Council in 1715. but Richard conformed to the Church of Ireland.