Carmarthen Priory was founded in the early 12th century as an Augustinian house, and grew into one of the most important monastic establishments in west Wales. It owned much of the land east of the medieval town, ran the local schools, and produced the Black Book of Carmarthen — the oldest surviving manuscript entirely in the Welsh language — around 1250.
The priory was dissolved by Henry VIII in 1539. The church was demolished within a few years, and most of the stone was carted away for use in new building elsewhere in the town. Today the site is a small grassed enclosure at the eastern end of Priory Street, with low remains of the cloister wall and a stone plaque commemorating the Black Book. Across the road is the site of Merlin's Oak.
It is a 15-minute walk east from the town centre and worth combining with a visit to the Moridunum Roman amphitheatre a few hundred metres further on.