The church of St Hywyn is situated on the south side of Aberdaron village, the graveyard running to the cliff edge. Its location in the centre of the broad sandy bay is typical of an early christian foundation. It was the most important church in Llyn being the embarkation point for pilgrims, and its clas, or monastery, was a place of sanctuary. The canons of St Hywyns provided a boat to Gruffydd ap Cynan for his escape to Ireland in c.1094 and gave sanctuary to Gruffydd ap Rhys of Deheubarth from Gruffydd ap Cynan and Henry I in 1115.

The church was probably rebuilt by Gryffydd ap Cynan of Gwynedd in the early twelfth century, with modifications dating from the fourteenth to sixteenth centuries. Restoration, after a long period of decline (which led to the building of a new church inland) was carried out in 1868 to designs of Henry Kennedy. Further work was done in the early twentieth century by John Williams of Bangor.

The present structure is built of rubble stone with slate roofs, coped gables and bellcote. It consists of a nave of two equal aisles, the northern one older (twelfth-century) with west single bellcote, and west arched doorway which is possibly twelfth-century but with fifteenth-century detail.
The spacious interior (refurbished in 2006) has stone walls (formerly plastered) beneath a restored hammerbeam roof of six bays. The arcade, of c.1500, is of pale gritstone and composed of five four-centred moulded arches on octagonal piers with moulded capitals and bases.

Fittings include a plain octagonal font on an octagonal shaft (c.1500), a stoup in the form of a plain oblong stone bowl (medieval), and an ornate timber pulpit and litany desk (1911).

Associated with:
Inscribed stones (Nprn 275721 and 275722)

(Sources: Inventory of the Ancient Monuments in Caernarvonshire, vol.III (RCAHMW); Cadw Listing description; R.Haslam, J.Orbach and A.Voelker, Buildings of Wales: Gwynedd (2009), p.227.)
RCAHMW 26.04.2018