St Cynhaearn's Church is a redundant church standing in an isolated position on Ynyscynhaearn, a former island in Llyn (Lake) Ystumllyn,[1] 900 metres (980 yd) south of the village of Pentrefelin, near Criccieth in Gwynedd, Wales.

[2] It is constructed in stone rubble, with the walls of the nave and the east side of the chancel being stucco.

[1] Dating from 1832, the pulpit is a three-decker, approached by nine steps, below which is a lectern with a reading shelf, and under this is the reader's desk.

[3] The chamber organ by Flight and Robson dates from 1834 and was given by a Mrs Walker; it cost £30 (equivalent to £3,642 in 2023).

[2] An earlier grave records the early passing of David Owen (1712–1741), a local blind composer and harpist who was known as "Dafydd y Garreg Wen" or David of the White Rock, as he came from Garreg Wen (White Rock) Farm.

[7] He was a black man brought back from Africa by a member of the Wynne family who lived at Ystumllyn, which can be seen from the church.

[3] There is a memorial to James Spooner (1790–1856), the surveyor who built the Ffestiniog Railway and members of his family, including his daughter, the novelist Louisa Matilda Spooner (1820–1886), in the form of a stone urn surrounded by iron railings.