Viscount Sarsfield, of Kilmallock, was a title in the Peerage of Ireland. It was created in 1627 for Sir Dominick Sarsfield, 1st Baronet, Chief Justice of the Irish Common Pleas. He had already been created a Baronet, of Carrickleamlery, in the Baronetage of Ireland in 1619. The second Viscount converted to the Roman Catholic faith, and is chiefly remembered for sheltering his cousin William Tirry, the future martyr. The titles were forfeit in 1691 by the fourth Viscount for his part in the Williamite war in Ireland. The title was often cited as "Sarsfield of Kilmallock" and since Sarsfield is a common name in Ireland the holder was often called "Lord Kilmallock" for convenience.