St. John's Priory, Medieval monastery and hospital near Trim, Ireland.

St. John's Priory is a medieval monastic complex in Trim featuring stone buildings constructed across several centuries. The site includes a church dating from the 1200s, multi-story structures, fortified walls with defensive towers, and a tower standing near the Boyne River.

Simon Rochfort, Bishop of Meath, founded St. John's Priory around 1202 for the Crutched Friars. The first written record dates from 1281, when alms were granted from the manor of Magathtreth. In 1540, at the Dissolution of the Monasteries, Robert Dillon received the priory, which then included a church, two towers, a hall, storehouse, kitchen, brewhouse, two granaries, a dovecote and a haggard, plus 90 acres of arable land near the Boyne.

The priory belonged to the Crutched Friars, a order whose hospitals were built like Canons Regular monasteries but with special facilities for caring for the sick. One building retains a chute that disposed of waste material into the Boyne, a detail of the infirmary's daily operation.

St. John's Priory stands about 1.6 km east of Trim town centre on the south bank of the Boyne, with Newtown Abbey just across the river to the northwest. The remains are those of a National Monument, so access is on foot through the open site rather than through a staffed visitor centre. The enclosing wall of the 15th–16th century, with its corner turret, and the three-storey vaulted tower help orient a walk around the ruins.

After closure in the 1500s, the property passed to private owners, and local stories tell of a soldier who fled after spending just one night there due to strange occurrences he witnessed. This tale has become part of the site's reputation among visitors.