Brabazon Ponsonby, 1st Earl of Bessborough (1679 – 4 July 1758) was a British politician and peer. He was the son of William Ponsonby, 1st Viscount Duncannon and Mary Moore. He was an active politician from 1705 to 1757 in Great Britain and Ireland. He represented Newtownards and County Kildare in the Irish House of Commons. He inherited his father's viscountcy in 1724 and was made Earl of Bessborough in the Peerage of Ireland in 1739. He is buried in Fiddown, County Kilkenny, Ireland.
Ponsonby married Sarah Margetson, an heiress whose family owned Bishopscourt, County Kildare, and his family remained there until the 1830s.