St. Mary's Abbey was a former Cistercian abbey located near the junction of Abbey Street and Capel Street in Dublin, Ireland. Its territory stretched from the district known as Oxmanstown down along the River Liffey until it met the sea. It also owned large estates in other parts of Ireland. It was one of several liberties that existed in Dublin since the arrival of the Anglo-Normans in the 12th century, which gave it jurisdiction over its lands.

The abbey was founded by the Irish king Máel Sechnaill mac Máele Ruanaid (died 862) in 846, according to the Annals of the Four Masters. It was originally Benedictine, but in 1139 was given by Malachy O'Morga, the legate of the Pope, to monks belonging to the Congregation of Savigny, which in 1147 joined the Cistercian order.