Castleton (Welsh: Cas-bach) is a hamlet in the city of Newport, South Wales.

Castleton is in the Marshfield ward on the A48 dual carriageway located between the city of Newport to the east and Cardiff to the west.

[1] This building is now used as a business and Church meetings are held at Gateway Baptist in Marshfield nearby.

The Great Western Railway station at nearby Marshfield acted as a rail connection, eastwards to Newport and onwards through the Severn Tunnel, terminating at London Paddington, and westwards to Cardiff and Fishguard Harbour.

Closed since 1959,[2] long before the Beeching cuts took effect, the nearest rail stations today are Newport and Rogerstone.