Llandysilio 3 is a fragmentary roman-letter inscribed stone, which was first noted in 1896. It may have come to light during the 1838 restoration of St Tysilio's Church, Llandysilio (NPRN 308656), when it was built into the external south wall of the church (east of the nave window), along with two other inscribed stones and a cross-carved stone.

The stone is a fragment of dacite. Other small fragments of the same material have been noted in the wall of the church and may represent reused pieces of the same inscribed stone. Only face A is visible. The fragmentary inscription reads 'RIAT' is thought to date to the 5th to 6th century.

Sources include:
Edwards, N. 2007, Corpus of Early Medieval Inscribed Stones and Stone Sculpture in Wales

N Vousden, 3 January 2018