Cornelius O'Callaghan, 1st Viscount Lismore PC (I) (2 October 1775 – 30 May 1857) was an Irish Whig[1] politician.
He succeeded to his father's title on 12 July 1797 and assumed his seat in the Irish House of Lords.
From 1806 to 1807 he sat in the House of Commons of the United Kingdom as a Member of Parliament (MP) for Lostwithiel, a rotten borough in Cornwall controlled by Lord Mount Edgcumbe.
[2] In 1838 he was made Baron Lismore in the Peerage of the United Kingdom, giving him and his descendants an automatic seat in the British House of Lords.
The 1st Viscount of Lismores son Cornelius O'Callaghan (1809–1849) who pre-deceased him, served as MP for Tipperary and Dungarvan in the House of Commons.