Ardfert Cathedral (Irish: Ardeaglais Ard Fhearta) is built on the site of a monastery founded in the 6th century by St. Brendan the Navigator. The cathedral is located in the village of Ardfert, County Kerry, Ireland. The site is now managed by the Office of Public Works. Part of the transept has been restored, and houses the entrance and a gift shop.
The cathedral has a Romanesque west doorway with outward pointing chevron decoration in the Anglo-Norman style. It is flanked by blind arcading with lozenge-stonework similar to that found in parts of south-west France. It also has a 13th-century east window and a row of nine lancets in the south wall. Two effigies of ecclesiastical figures of the late 13th- or early 14th-century period are mounted on either side of the east window. The battlements were added in the 15th century. The pre-12th century block of masonry is clearly visible in the north wall. One of the two smaller churches is a fine example of late Romanesque and the other is a plain 15th century structure with a carving of a wyvern on one of the windows. In the north-east corner is a double rectangular niche containing a grotesque head with lips pulled back to reveal large teeth. This may be a variant of the 'mouth-puller' motif often found in Spain and western France.
To the north-west of the cathedral itself is Temple-na-hoe, a late Romanesque church, whose chancel has now disappeared. It has decorated three quarter columns instead of antae at each cornerstone, with heads and bird motifs on the capitals. A cornice decorated with spiral bosses supports the roof. The west doorway is plain, but the south window has floral ornament and the chancel arch has chevron ornament.
Further to the north-west is a 15th-century church, Temple-na-Griffin, after the carvings of wyverns inside the windows of the north wall.
The site has three medieval church ruins, the earliest building being from the 12th century, with additions made in the 15th century when a small transept was added and battlements were constructed, an ogham stone and a number of early Christian and medieval grave slabs. The cathedral roof was destroyed during the Irish Rebellion of 1641, but the south transept was re-roofed and extended later in the 17th century when it was converted into a Protestant Church. In 1871, when a new Protestant church was opened, the roof was again removed. Within the adjoining graveyard there are two other churches Temple Na Hoe dating from the 12th century and Temple Na Griffin dating from the 15th century.