Sarn Gynfelyn

Sarn Gynfelyn (or Sarn Cynfelyn) is a shingle spit on the coast of Cardigan Bay, in the county of Ceredigion, Mid-Wales, in the United Kingdom. It is located at Wallog, a few kilometres north of Llangorwen, close to Clarach Bay, south of Borth and north of the town of Aberystwyth. It extends, albeit with a single break, for a distance of 11km from the coast to a reef known as Patches or Caerwyddno.

Similar landform examples are found at several points along the Cardigan Bay coast, known as sarnau. 'Sarn' (pluralised in Welsh as 'sarnau') is typically translated as 'causeway' or 'paved way'. These long banks which extend from the intertidal zone to the subtidal zone are thought to have originated as glacial moraines.