Llanwinio Church was founded by St. Gwinio in the sixth century. The present Victorian building was built on the foundations of the Celtic building. Whilst the foundations were being built for the present church a stone with an inscription in Ogam was found. The inscription translates as Bivadus, son of Bodibeva. The form of the letters date it to the late 5th - 6th century and it is now in the Carmarthen Museum. There is also a very interesting stone built into the wall of the porch.

Although now relatively isolated, Llanwinio was probably on the main highway between Ireland and England in the sixth century. St. Gwynio also founded a chapel at Cilsant some four miles away (the name means Saint's Retreat) and would walk from here along a footpath to the church at Llanwinio. He was attacked by Irish marauders on this path and decapitated. A spring sprung from the ground where his head fell, probably at Ffynnon Felyn. His Saint's day is the 2nd of May and in 1994 a pilgrimage was held to retrace his steps from Cilsant to Llanwinio Church.