Bletherston (Welsh: Trefelen) is a small settlement and parish in Pembrokeshire, Wales.

The Welsh placename Trefelen means "yellow farm".

[1] The church of St Mary, in the centre of the village, is a grade II* listed building, parts of which may be 12th century, but have been added to or altered since.

[2][3] The parish,[4] which was noted on a map of 1583,[5] is in the north-west portion of the hundred of Dungleddy which George Owen in 1602 placed south of the Pembrokeshire language frontier.

However, as part of the church lands to the north of the Afon Syfynwy, Owen said it was bilingual, and in modern times it has been predominantly Welsh-speaking.