Llanfair Caereinion is a small town in Powys, east central Wales upon the River Banwy (also known as the River Einion), around 8 miles west of Welshpool.
In 2001 it had a population of 1,616. The town is built upon the site of an old Roman fort. Llanfair is most famous for being a terminus of the Welshpool and Llanfair Light Railway.