Upper Ossory was formerly an administrative barony in the south and west of Queen's County (now County Laois) in Ireland. In late Gaelic Ireland it was the túath of the Mac Giolla Phádraig (Fitzpatrick) family and surviving remnant of the once larger kingdom of Ossory. The northernmost part of the Diocese of Ossory and medieval County Kilkenny, it was transferred to the newly created Queen's County in 1600. In the 1840s its three component cantreds, Clarmallagh, Clandonagh, and Upperwoods, were promoted to barony status, thereby superseding Upper Ossory.
County Kilkenny was created after the Norman invasion of Ireland from most of the Gaelic Kingdom of Ossory. Kilkenny's medieval cantred of Aghaboe, whose territory was the rural deanery of Aghaboe, corresponded approximately to the later Upper Ossory. From 1328, the Anglo-Norman Butler Earl of Ormond had palatine jurisdiction over the neighbouring county of Tipperary, and in the 15th century, the Butlers extended this de facto to most of Kilkenny. This was reflected in the subsidiary title Earl of Ossory which Piers Butler, 8th Earl of Ormond was granted in 1538. However, in the 14th and 15th centuries, the Gaelic Fitzpatrick family (Irish: Mac Giolla Phádraig) encroached southwards into Kilkenny and ruled as "Lords of Upper Ossory". In 1442, the Irish Treasury and Exchequer were petitioned to award the inhabitants of the town of Kilkenny 100s for the resistance against the neighbouring Irish and "especially in breaching the castle of McKilpatrick [sic]".
In 1541, during the Tudor reconquest of Ireland, Barnaby Fitzpatrick (Brían Óg Mac Giolla Phádraig) was created 1st Baron Upper Ossory upon the surrender and regrant of his lands to and by Henry VIII, legitimating his lordship in the eyes of the Dublin Castle administration. Queen's County was created in 1556 from unshired lands northeast of Upper Ossory. In 1575, Henry Sidney, then Lord Deputy of Ireland, wrote "Upper Osserie is so well governed and defended, by the valor and wisedome of the Baron that nowe is as ... it made no matter, if the countrie were never shired, ... and yet united to some shire it shal be". Fitzpatrick preferred to be subject to the new English planters in Queen's County rather than his Ormond enemies in Kilkenny. By letters patent of 21 July 1600 Upper Ossory was formally transferred to Queen's County.
An exception was made for an area around Durrow, which remained an exclave of the Kilkenny barony of Galmoy. This was at the behest of the Earl of Ormond, who was lord of the manor of Durrow, and wanted to have Fitzpatrick raiders tried at the assizes of Kilkenny, where he could ensure a conviction. 
After Arthur Chichester was made Lord Deputy in 1605, the lordship of the Fitzpatricks effectively ended. A 1621 inquisition in Maryborough (now Port Laoise) ruled that the king, James I, was lord of Upper Ossory, and he proceeded to grant George Villiers, 1st Duke of Buckingham extensive lands in the barony. As late as 1639, a statute refers to "upper Ossory, alias Mac Gil Patricks country".
Upper Ossory comprised one third of the territory of Queen's County. From the time of the Down Survey it was for many purposes divided into three subunits called cantreds; namely Clarmallagh, Clandonagh, and Upperwoods. The Ordnance Survey of Ireland's first edition maps of 1836–42 regarded these as baronies superseding Upper Ossory, as did the 1841 census. The Valuation of Lands (Ireland) Act 1836 empowered the grand jury of a county to subdivide large baronies. Whereas an order in council of 22 December 1841 refers to "that part of the barony of Upper Ossory, in the Queen's County, which is commonly called the Cantred of Clarmallagh, and which, according to the ordnance survey, is named the barony of Clarmallagh", another order in council of 9 February 1842 refers simply to "the barony of Clarmallagh". The 1846 Parliamentary Gazetteer recorded Upper Ossory as having been "a few years ago practically abolished".
The Redistribution of Seats Act 1885 split the two-seat constituency of Queen's County into two single-seat constituencies, one of which was to be called "Upper Ossory division"; this was changed to "Ossory division" at the committee stage by Richard Lalor, who said "there were both an Upper and a Lower Ossory at one time, but there was no distinction between the two now". The constituency comprised not just the former Upper Ossory but also Maryborough West, Tinnahinch, and part of Portnahinch.
The name of the town of Borris-in-Ossory recalls its location in Upper Ossory.
|Baron Upper Ossory||Ireland||Barnaby||1541||Barnaby (7th)||1791||Attainted 1791, died 1796.|
|Earl of Upper Ossory||Ireland||John||1751||John (2nd)||1818||Previously Baron Gowran|
|Baron Upper Ossory, of Ampthill in the County of Bedford||Great Britain||John||1794||John (1st)||1818||The 2nd Irish Earl was the first and only British Baron.|
|Baron Castletown, of Upper Ossory in the Queen's County||United Kingdom||John (Wilson)||1869||Bernard (2nd)||1937||John Wilson assumed the surname of his father, the second Earl, upon legitimation. Castletown is a village in Upperwoods, Upper Ossory.|
- Collins, Arthur; Brydges, Sir Egerton (1812). "Fitzpatrick, Lord Upper Ossory". Peerage of England: Genealogical, Biographical, and Historical. Greatly Augmented and Continued to the Present Time. Vol.8. Printed for F. C. and J. Rivington. pp. 295–9. Retrieved 15 October 2012.
- Edwards, David. "Collaboration without Anglicization: The Macgiollapadraig Lordship and Tudor Reform." Gaelic Ireland c. 1250-c.1650: Land, Lordship, & Settlement. Ed. Patrick J. Duffy, David Edwards, & Elizabeth FitzPatrick. Dublin: Four Courts Press, 2001. pgs. 77-97. Print.
- Edwards, David (September 2003). The Ormond lordship in County Kilkenny, 1515-1642: the rise and fall of Butler feudal power. Four Courts Press. Retrieved 13 October 2012.
- Empey, C. A. (1971). "The Cantreds of the Medieval County of Kilkenny". Journal of the Royal Society of Antiquaries of Ireland. Royal Society of Antiquaries of Ireland. 101 (2): 128–134. JSTOR 25549764.
- Quinn, D. B.; Nicholls, K. W. (2009-05-03). "Ireland in 1534". In Moody, T. W.; Martin, F. X.; Byrne, F. J. Early Modern Ireland 1534-1691. A New History of Ireland. Vol.3. Oxford University Press. p. 8. ISBN 9780199562527. Retrieved 13 October 2012.
- Crooks, Peter (1 July 1442). "Close Roll 20 Henry VI [RCH 263] No.23". CIRCLE: A Calendar of Irish Chancery Letters, c. 1244–1509. Trinity College Dublin. Retrieved 10 November 2017.
- Collins & Brydges 1812, p.295
- Maginn, Christopher (2012-03-15). William Cecil, Ireland, and the Tudor State. Oxford University Press. p. 193. ISBN 9780199697151. Retrieved 14 October 2012.
- Atkinson, Ernest George (1903). "Vol.ccvi Part 4 No.41". Elizabeth: 1600 March - October. Calendar of the State Papers relating to Ireland, of the reigns of Henry VIII, Edward VI., Mary, and Elizabeth. 9. London: HMSO. p. 328.
- Collins & Brydges 1812, p.299
- Nicholls, K. W. (May 19, 2011). "Map 45: Counties 1542-1613". In Moody, T. W.; Martin, F. X.; Byrne, F. J. Maps, Genealogies, Lists: A Companion to Irish History, Part II. A New History of Ireland. Vol.9. Oxford University Press, USA. p. 43. ISBN 019959306X.
- Carrigan, William (1905). The history and antiquities of the diocese of Ossory. Vol.2. Dublin: Sealy, Bryers & Walker. p. 220.
- Phelan, Margaret M.; Kirwan, John (1997). Kilkenny: studies in honour of Margaret M. Phelan. Kilkenny Archaeological Society. p. 62. Retrieved 13 October 2012.
- Edwards, David (1999). "The MacGiollapadraigs (Fitzpatricks) of Upper Ossory, 1532-1641". In Pádraig G. Lane and William Nolan. Laois: History & Society. Geography Pubs.
- 15 Charles I c.6 sec.2. Statutes Passed in the Parliaments Held in Ireland. Vol.I. G. Grierson. 1794. p. 319. Retrieved 14 October 2012.
- Robert C. Simington, ed. (1961). "Barony Boundaries 26. The Barony of Upper Ossory". Miscellanea. The Civil Survey 1654-6. Vol.X. Irish Manuscripts Commission. p. 23.
- "County (Ireland)". Statutory rules and orders other than those of a local, personal, or temporary character. Vol.II. H.M.S.O. 1904. pp. 60–61. Retrieved 10 March 2017.
- "Queen's County". Report of the commissioners appointed to take the census of Ireland, for the year 1841. Command papers. XXIV (504). HMSO. 1843. pp. vi,106, 108.
- 6 & 7 Will 4 c.84
- "Queen's County". The Parliamentary Gazetteer of Ireland: Adapted to the New Poor-law, Franchise, Municipal and Ecclesiastical Arrangements, and Compiled with a Special Reference to the Lines of Railroad and Canal Communication, as Existing in 1844-45. Vol.III. A. Fullarton and Company. 1846. p. 100.
- HC Deb 21 April 1885 vol 297 c365
- O'Hart, John (1892). "FitzPatrick (No.1) Princes of Ossory". Irish Pedigrees; or the Origin and Stem of the Irish Nation.
- "Castletown". Placenames Database of Ireland. Retrieved 13 October 2012.