Baron Killeen and Earl of Fingall were titles in the Peerage of Ireland. Baron Fingall was a title in the Peerage of the United Kingdom. The seat of the title-holders was, from establishment until 1953, Killeen Castle in County Meath, Ireland, and there was an ongoing close relationship with the related Plunkett family of Dunsany, and with the Viscounts Gormanston, who intermarried. Around 1426, Christopher Plunkett was created Baron Killeen: his seven sons founded five separate branches of the Plunket family, including the Plunkets of Dunsany, Rathmore and Dunsoghly. The tenth baron, Luke Plunkett, was created Earl of Fingall on 29 September 1628. When still Baron Killeen, his first wife was Elizabeth, the second daughter of Henry FitzGerald, 12th Earl of Kildare, as properly recorded in the histories of the FitzGeralds of Kildare, based on their own family archives in Carton House and Kilkea Castle, and on no better authority than the 4th Duke of Leinster himself, writing at the time as Marquis of Kildare who confirmed that Elizabeth married Luke Plunkett, the first Earl of Fingall in 1608,.
The eighth earl was created Baron Fingall on 20 June 1831. All three titles became extinct on the death of the twelfth earl in 1984, and are not to be confused with the Prescriptive Barony or Lordship of Fingal originally granted in 1208 by King John of England. See also Fingal.
The Earls' of Fingall’s Fingall Estate Papers (i.e. real property) consist of a large archive of manuscripts and ephemera (17th–20th century), documents incl. deeds, indentures, leases, wills, marriage settlements, incl. many on vellum. The Papers were purchased by the Fingal County Council and lodged in its Fingal Local Studies and Archives Department following an auction by Whyte’s Auctioneers on 6 February 1999 (item 373). However, the lands concerned did not actually extend into Fingal, and the Earls’ Fingall Estate Papers contain no evidence of any ownership in Fingal. Practically all the properties and leases relate to County Meath (or Westmeath), understandably since the Plunketts were originally, as indicated above, Barons of Killeen in County Meath. They essentially have nothing to do with the territory of Fingal, and hence the lands per se never justified the denomination of Fingall as an Earldom and later peerage Barony (both now extinct) for the Plunketts of Killeen in Meath (as the prescriptive barony of Fingal rested with the Viscounts Gormanston by descent from Walter de Lacy who obtained it in 1208). Rather, the evidence indicates that Lord Killeen negotiated and purchased the Earldom for £2,700 during a sojourn in London in 1628.