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.

Brut y Tywysogion states that the church was sacked by Vikings in 963, and during the twelfth century it was the subject of a memorable poem by Llywelyn Fardd (I). The earliest parts of the building date to the twelfth century, and it originally had a central tower, although this fell down in 1693.^[1]

The church houses two fourteenth-century monuments. One of the effigies is of an unknown priest in full Eucharistic vestments. The other is a military figure thought to be Gruffudd ab Adda (d. c. 1350) of Dôl-goch and Ynysymaengwyn. The effigy is known as the 'Crying Knight' due to a flaw in the stone at his right eye which becomes damp during wet weather, giving the impression of weeping.^[2]

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'.^[3] National Street (formerly Duck Street) was named after the National School, later Towyn Church School, which was once located on the street.