Coordinates: 52°02′N 4°28′W / 52.04°N 4.47°W / 52.04; -4.47
Newcastle Emlyn (Welsh: Castellnewydd Emlyn) is a town straddling the border of the counties of Ceredigion and Carmarthenshire in west Wales and lying on the River Teifi; it is also a community entirely within Carmarthenshire. The community is bordered by the communities of Llangeler and Cenarth, both being in Carmarthenshire; and by Llandyfriog in Ceredigion.
Adpar is the part of the town that lies on the Ceredigion side of the River Teifi. It was formerly called Trefhedyn and was an ancient Welsh borough in its own right.
The town takes its name from the cantref of Emlyn which was an administrative district in Medieval Dyfed. The cantref was made part of the Norman March in the 12th century.
Notable buildings in the town include a ruined 13th-century castle, first mentioned in Brut y Tywysogion in 1215, when it was seized by Llewelyn the Great (Welsh: Llywelyn Fawr). The castle was captured by the Welsh during the revolt of 1287-8 and also by Owain Glyndŵr in 1403.
Coordinates: 52°01′59″N 4°26′06″W / 52.033°N 4.435°W / 52.033; -4.435
Emlyn was one of the seven cantrefi of Dyfed, an ancient district of Wales. It became part of Deheubarth in around 950. It consisted of the northern part of Dyfed bordering on the River Teifi. Its southern boundary followed the ridge of the line of hills separating the Teifi valley from the valleys of the Tâf and Tywi.
The name derives from am (around, on both sides of) and glyn (valley), the valley in question being presumably the Cuch. Its area was about 217 km2. It was divided by the River Cuch into the commotes of Emlyn Is Cuch (to the west) and Emlyn Uwch Cuch to the east. Its civil headquarters were divided between Cilgerran in the lower commote and Newcastle Emlyn in the upper. Its ecclesiastical centre (and perhaps, in the Age of the Saints, the seat of a bishop) was the church of St Llawddog at Cenarth.
The cantref was made part of the Norman March in the 12th century, and many castles were built, including those of Cilgerran and Newcastle Emlyn. Nevertheless, the area remained Welsh speaking, as it continues today.