Earl Landaff, of Thomastown in the County of Tipperary, was a title in the Peerage of Ireland. It was created in 1797 for Francis Mathew, 1st Viscount Landaff, who had previously represented County Tipperary in the Irish House of Commons. He had already been created Baron Landaff, of Thomastown in the County of Tipperary, in 1783, and Viscount Landaff, of Thomastown in the County of Tipperary, in 1797, also in the Peerage of Ireland. In 1800 he was elected as one of the 28 original Irish Representative Peers. He was succeeded by his son, the second Earl. The titles became extinct on his death in 1833. Thomastown Castle was the childhood home of Father Theobold Mathew, "The Apostle of Temperance".