Henry Ponsonby was the younger brother of Brabazon Ponsonby, 1st Earl of Bessborough.  He served in the Irish House of Commons as a Member of Parliament for Fethard in County Tipperary.  He was a Colonel in the 37th Regiment of Foot, and died at the Battle of Fontenoy in 1745, along with one of his fellow Hellfire Club members,  Henry Clements.