Earl of Bessborough is a title in the Peerage of Ireland. It was created in 1739 for Brabazon Ponsonby, 2nd Viscount Duncannon, who had previously represented Newtownards and County Kildare in the Irish House of Commons. In 1749, he was given the additional title of Baron Ponsonby of Sysonby, in the County of Leicester, in the Peerage of Great Britain, which entitled him to a seat in the British House of Lords. The titles Viscount Duncannon, of the fort of Duncannon in the County of Wexford, and Baron Bessborough, of Bessborough, Piltown, in the County of Kilkenny, had been created in the Peerage of Ireland in 1723 and 1721 respectively for Lord Bessborough's father William Ponsonby, who had earlier represented County Kilkenny in the Irish House of Commons.

The Peerage of Ireland consists of those titles of nobility created by the English monarchs in their capacity as Lord or King of Ireland, or later by monarchs of the United Kingdom of Great Britain and Ireland. It is one of the five divisions of Peerages in the United Kingdom. The creation of such titles came to an end in the 19th century. The ranks of the Irish peerage are duke, marquess, earl, viscount and baron. As of 2016, there were 135 titles in the Peerage of Ireland extant: two dukedoms, ten marquessates, 43 earldoms, 28 viscountcies, and 52 baronies. However, these titles have no official recognition in the Republic of Ireland, with Article 40.2 of the Constitution of Ireland forbidding the state conferring titles of nobility and stating that an Irish citizen may not accept titles of nobility or honour except with the prior approval of the Irish government.