MAHON, Sir Ross, 1st bt. (1763-1835), of Castlegar, co. Galway

Published in The History of Parliament: the House of Commons 1820-1832, ed. D.R. Fisher, 2009
Available from Cambridge University Press



1820 - June 1820

Family and Education

b. 2 Sept. 1763, 1st s. of Ross Mahon of Castlegar and Lady Anne Browne, da. of John, 1st earl of Altamont [I]. educ. Trinity, Dublin 1780. m. (1) 6 Aug. 1786, his cos. Lady Elizabeth Browne (d. 24 Feb. 1795), da. of Peter, 2nd earl of Altamont [I], 5da. (1 d.v.p.); (2) 1 Sept. 1805, Diana (d. 2 Dec. 1807), da. of Edward Baber of Park Street, Grosvenor Square, Mdx., s.p.; (3) 1 Oct. 1809, Mary Geraldine, da. of James Fitzgerald† of Inchicronan, co. Clare, 5s. 7da. suc. fa. 1788; cr. bt. 14 Apr. 1819. d. 10 Aug. 1835.

Offices Held

MP [I] 1798-1800.


The Mahons were in possession of the Castlegar property by 1696. Bryan Mahon (d. 1719) was for many years the homme d’affaires of the earls of Clanricarde. His son and heir Ross Mahon died in 1767 and was succeeded by his eldest son and namesake, who had married into the Browne family, subsequently earls of Altamont (1771) and marquesses of Sligo (1800). Two years before his death in 1788 his eldest son Ross, this Member, strengthened the alliance by marrying a daughter of his maternal uncle, the 2nd earl. His next brother John married her sister, while his sister Anne married Denis Browne*, Altamont’s younger son. After the death of his first wife Mahon sat for Granard for two years in the Irish Parliament as a pro-Union ministerialist.1 A brief and childless second marriage followed. In 1809 he married the sister of William Vesey Fitzgerald*, subsequently the close friend and ministerial colleague of Robert Peel*, who was Irish secretary from 1812 to 1818. In January 1816 Peel accepted Mahon’s invitation to stay at Castlegar during his break from business in Dublin, but he declined to repeat the experience the following year.2 Mahon, whose annual rental was about £10,000 in 1809, about a quarter of which may have come from his Galway property, received a baronetcy in 1819.3 At the general election the following year he was returned in his absence, apparently as a seat-warmer, for the close borough of Ennis, where it was the Fitzgeralds’ turn to nominate the Member.4 It seems unlikely that he took his seat, for only three months later he made way for one of the Wellesleys. He died in August 1835. His eldest son Ross, an army officer, died unmarried in 1842, as did his second son James, a lawyer, in 1852, when the baronetcy passed to his third son William Vesey Mahon (1813-93), rector of Rawmarsh, Yorkshire.

Ref Volumes: 1820-1832

Author: Stephen Farrell


  • 1. Hist. Irish Parl. v. 180.
  • 2. Add. 40250, ff. 182, 184; 40261, ff. 248-9.
  • 3. Hist. Irish Parl. v. 180; Analecta Hibernica, xxv (1967), 91.
  • 4. Dublin Weekly Reg. 25 Mar. 1820.