St Cadfan's Church (Welsh: Eglwys Cadfan) is situated in Tywyn in the county of Gwynedd, formerly Merionethshire, Wales. The church is noted for its Romanesque architecture and for housing the Cadfan Stone, a stone cross dating from ninth century or earlier which is inscribed with the oldest known written Welsh. The vicarage, which was built in the early 19th century, still stands on National Street. It is now a private house called 'Tŷ Cadfan Sant'. National Street (formerly Duck Street) was named after the National School, later Towyn Church School, which was once located on the street.