Trevethin or Trefethin (Welsh: Trefddyn) is a suburb of Pontypool and a community in Torfaen, Wales.

It includes two electoral wards (Trevethin and St Cadocs and Penygarn) for Torfaen County Borough Council.

It has become a modern suburb, as economic growth led to a construction boom surrounding the village in the 1960s and '70s.

Trevethin is situated in Pontypool and is on the southernmost point of the Brecon Beacons National Park.

Near to Trevethin are various famous landmarks including the Folly Tower and Shell Grotto both of which were originally built by the Hanbury family during the 18th century.