Bletherston (Welsh: Trefelen) is a hamlet and parish in Pembrokeshire, Wales. It is situated in the middle of the county, 9 km north of Narberth and 13 km east of Haverfordwest. The parish includes the village of Penffordd 51°52′0″N 4°47′39″W / 51.86667°N 4.79417°W. Together with the parishes of Llys y Fran and New Moat, it constitutes the community of New Moat.
The church of St Mary's in the centre of the village is a grade II* listed building.
The English placename appears to mean Bleddri's farm: Bleddri is a Welsh name. The Welsh placename Trefelen means "yellow farm". The parish 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.