Newcastle Emlyn (Castell Newydd Emlyn) is a town, straddling the counties of Ceredigion and Carmarthenshire in west Wales (though officially it is in Carmarthenshire), lying on the River Teifi. The part of the town that lies on the Ceredigion side of the River Teifi is Adpar, formerly called Trefhedyn and was an ancient borough in its own right. The town gets its name from the cantref of Emlyn, of which it was the administrative centre.
Notable buildings in the town include the remains of the thirteenth century castle, first mentioned in Brut y Tywysogion in 1215, when it was seized by Llywelyn ap Iorwerth; the town hall and the secondary school, Ysgol Gyfun Emlyn. Other attractions include an art gallery and theatre, the Attic Theatre, while the Museum of the Welsh Woollen Industry and the Teifi Valley Railway lie nearby.
Unlike many small rural towns across Wales, Newcastle Emlyn has managed to maintain a wide range of local services, based mainly on small family businesses. Reflecting the agricultural nature of the area, the Saputo factory, which manufactures Mozzarella cheese, is the town's biggest employer.
Into the 1960s, well over 90% of the town's population was Welsh-speaking, but a constant flow of incomers from outside Wales has had a marked effect on the town's linguistic make-up. Nevertheless, Welsh remains the language of most of the town's inhabitants and is spoken by 90% of those who are Welsh-born. According to the United Kingdom Census 2001, the population of Newcastle Emlyn was 941 people, of whom 69% speak Welsh fluently. Taken together with Adpar on the Ceredigion side of the river Teifi the town's population is approximately 1,500 people.