Plas Llanstephan is a mansion in the county of Carmarthenshire, Wales. It is set well back from the public road among pasture fields and is reached by a private driveway from the village of Llansteffa

Carmarthenshire is a county in the south-west of Wales. The three largest towns are Llanelli, Carmarthen and Ammanford. Carmarthen is the county town and administrative centre. The county is known as