Cwmerfyn (historically Cwm-erfin or Cwmerfin) is a hamlet in the community of Trefeurig, Ceredigion, Wales, nine miles (14 km) by road east of Aberystwyth.

[1] Cwmerfyn is represented in the Senedd by Elin Jones (Plaid Cymru) and is part of the Ceredigion constituency in the House of Commons.

[4][5] Siloa Chapel in Cwmefyn was built in 1866, as part of a series of churches founded by Azariah Shadrach in north Ceredigion in the Congregational Church of Salem Coedgruffydd.

[6] The chapel is described by Coflein as having a "simple round-headed style, with a rendered exterior and slate roof with bracketed eaves".

[7] Cwmerfin lead mine is of prehistoric origin and was owned in the first half of the seventeenth century by Sir Hugh Myddelton (1560–1631) and Thomas Bushell (c.1593–1674).