Cornelius O'Callaghan, first son and heir of Thomas O'Callaghan of Shanbally, County Tipperary was born on 7 January 1740/1 and was M.P. for Fethard in four parliaments between 1761 and 1785. On 27 June 1785 he was created Baron of Lismore of Shanbally and as such the O'Callaghans were one of the very few native families to be dignified by the peerage of Ireland. He married Frances, granddaughter of the 3rd Duke of Devonshire and died on 12 July 1797, aged 56. The peerage became extint in 1898.
A slightly larger portrait of O'Callaghan, aged in his thirties, measuring 10 3/8 x 8 3/8 in. (26.3 x 21.3 cm.) was with The Leger Galleries Ltd., London, no. 64.