Barony Castletown
Sable a saltire argent, on a chief azure three fleur-de-lis or, all within a bordure wavy of the second
Creation date	10 December 1869
Created by	Queen Victoria
Peerage	Peerage of Ireland
First holder	John FitzPatrick
Last holder	Bernard FitzPatrick, 2nd Baron Castletown
Remainder to	First baron's heirs male of the body lawfully begotten
Extinction date	29 May 1937
Former seat(s)	Granston Manor, County Laois Templemore, County Tipperary
Motto	Fortis sub forte fatiscet ("The strong will yield to the strong")

Baron Castletown, of Upper Ossory in the Queen's County, was a title in the Peerage of the United Kingdom. It was created on 10 December 1869 for John FitzPatrick, the former Liberal Member of Parliament for Queen's County.^[1] He was the illegitimate son of John FitzPatrick, 2nd Earl of Upper Ossory.^[2]

The barony became extinct upon the death of his son, the 2nd Baron, on 29 May 1937. He had married Hon. Ursula Emily Clare St. Leger, daughter of the fourth Viscount Doneraile, but they had no children^[3][4]

• John Wilson FitzPatrick, 1st Baron Castletown (1811–1883)
• Bernard Edward Barnaby FitzPatrick, 2nd Baron Castletown (1849–1937)

• Earl of Upper Ossory

• Hesilrige, Arthur G. M. (1921). Debrett's Peerage and Titles of courtesy. London: London: Dean & son, limited. p. 183.
• The Fitzpatrick – Mac Giolla Phádraig Clan Society
• Fitzpatrick Arms, Crests, Mottos and Supporters by Ronan Fitzpatrick
• Descendants of Bryan Fitzpatrick, Lord and First Baron of Upper Ossory by Ronan Fitzpatrick and Steve Zalewski
• The Fitzpatrick Mythology by John Hylas Smith