Lancaster Priory, formally the Priory Church of St Mary, is a Church of England parish church. It is located near Lancaster Castle.

In 1094 Roger de Poitou established a Benedictine priory dedicated to St Mary, as a cell of the Abbey of Saint Martin of Sées in Normandy, France. Around 1360 the nave was widened to about 49 feet (15 m). In 1431 the church was transferred from Sées to Syon Abbey near London after which there was a major reconstruction in the Perpendicular style.

A restoration of the church occurred in 1558. There were further changes made in the 18th through 21st centuries.