The ruined church at Grangefertagh, Co. Kilkenny, was at various points a monastery, a Protestant parish church, an abandoned shell, and finally a venue for a very different kind of congregation. When the roof collapsed around 1780, the building was eventually adapted as a ball-alley, a local term for a handball court, and the interior walls were coated in concrete to create the smooth surface the game requires. That render survives, sealing whatever medieval stonework lies beneath. The walls were also raised by roughly a metre and a half to suit the sport, and you can still read the join between the original medieval masonry and the later addition if you look carefully at the exterior.

The site sits on a natural rise above the marshy flood plain of the River Goul, on ground that was almost certainly sacred long before the priory existed. The monastery here is thought to have been founded by St Ciarán of Sir in the 6th century, though the priory itself was established in the 13th century by the Blanchfield family for the Canons Regular of St Augustine, a reforming order that followed a rule derived from the writings of St Augustine of Hippo. The community appears in documentary records from 1251. By 1421, things had deteriorated badly: a papal record notes that the priory had been so destroyed by wars and other disasters that the canons were wandering and begging for food. By 1455 the house was described as very poor, though it was still functioning and maintaining hospitality. That same year, a dispute over the priorship saw one Thady Megirid, who had repaired the buildings, challenged by a rival canon, Thady Ocrinam, who had simply installed himself. The priory was suppressed in 1540, and a survey the following January recorded its possessions as sixty acres, three cottages, and two rectories, with the last prior, Robert Sortall, receiving a modest pension. The site passed through the hands of Sir Edward Butler and then James Butler Jr. in the 1560s. After the Reformation the church served Protestant congregations from the reign of Elizabeth I until around 1731, then was repaired and used until the roof gave way. Its ornamental doorway and tracery windows were subsequently stripped out: the west doorway and east window were removed in 1799 and rebuilt into the Church of Ireland church in Johnstown, and another window followed in 1832.

A round tower stands about 20 metres to the south-west of the church, a reminder of the early medieval monastery that preceded everything else on this hill. Attached to the north wall of the church is the Kilpatrick chapel, built by the MacGillapatrick family in the 15th or early 16th century, which contains an effigial tomb and a graveslab dating to the 13th or 14th century. Heavy ivy growth obscures much of the exterior stonework, but the embrasure of a two-light ogee-headed window, its arched head shaped in a gentle S-curve characteristic of late medieval Irish Gothic, is visible towards the north end of the east wall.