George Ponsonby O'Callaghan, 2nd Viscount Lismore (16 March 1815 – 29 October 1898) was an Irish peer and British Army officer.
On 30 May 1857 he succeeded to his father's titles and assumed his seat in the House of Lords.
He also succeeded his father as Lord Lieutenant of Tipperary and held the position until 1885.
He married Mary Norbury, daughter of George Norbury of Fulmer, Buckinghamshire, on 25 July 1839, and together they had two sons: Both sons predeceased Lord Lismore, leaving no heir, and his titles became extinct upon his death.
The Lismores had a home in Ireland at Shanbally Castle and also in Mayfair, London.