Richard FitzWilliam, 6th Viscount FitzWilliam (24 July 1711 - 25 May 1776), KB, PC, FRS, of Mount Merrion, near Dublin, Ireland, was an Anglo-Irish peer and property developer.
He was a grandson of Sir John Shelley, 3rd Baronet. He served as the Vice-Admiral of Leinster and was elected a Fellow of the Royal Society. He temporarily moved to Richmond Green in Surrey, but eventually returned to his family's principal seat in Mount Merrion, near Dublin.
He was the eldest son and heir of Richard FitzWilliam, 5th Viscount FitzWilliam by his wife Frances Shelley, a daughter of Sir John Shelley, 3rd Baronet and his first wife Bridget Nevill.
He replaced his father as Vice-Admiral of Leinster in 1728. He succeeded his father in the viscountcy in 1743 and took his seat in the Irish House of Lords. He was created a Knight Companion of the Order of the Bath (KB) in 1744 and was elected a Fellow of the Royal Society in 1747. [1] He was sworn of the Irish Privy Council in 1766. He lived for a time at Richmond Green in Surrey with his father-in-law Sir Matthew Decker, 1st Baronet, but later moved back to Mount Merrion, the family's principal seat near Dublin.
On 3 May 1744, he married Catherine Decker, eldest daughter and co-heiress of Sir Matthew Decker, 1st Baronet, a wealthy merchant of Dutch origin, by his wife Henrietta Watkins, at Sir Matthew's house in St James's Square. [2] Horace Walpole thought the marriage notable enough to mention in his correspondence. [3] By Catherine he had issue including:
Lord FitzWilliam died on 25 May 1776 at Mount Merrion and was buried at Donnybrook Cemetery.