Inislounaght Abbey (Irish: Mainistir Inis Leamhnachta - "monastery on the island of fresh milk"), also referred to as Innislounaght, Inislounacht and De Surio, was a 12th-century Cistercian settlement on the river Suir, near Clonmel in County Tipperary, Ireland.

[2] The abbey was refounded between 1142 and 1148 on lands donated by Malachy O'Phelan, lord of the Decies (part of which was in present-day County Waterford), and Donald O'Brien, king of Munster.

That in the same quarter of Tipperary, how James Butler, Abbey of Inislounaght and Dean of Lismore, hath sundry times disobeyed the King's writ and is a man of odious life, taking yearly and daily men's wives and burgess' daughters and keepeth no divine service but spends the goods of his church in voluptuosity, and mortgages the lands of his church and so the house is all decayed , and useth coyne and livery.

According to literary historian Patrick Leo (PL) Henry, Inislounaght may have been the inspiration for the fourteenth-century scathingly satirical poem Land of Cokaygne.

And O Faolain, who came from that stock, was king of Deise Thuaisceirt; and the place in which his residence was situated was on the brink of the Siuir to the west of Inis Leamhnachta; and Dun Ui Fhaolain is the name it is called to-day.