Pont Y Bermo/Barmouth Bridge, or Barmouth Viaduct is a Grade II* listed single-track wooden railway viaduct across the estuary of the Afon Mawddach near Barmouth, Wales. It is 820 metres long and carries the Cambrian Line. It is the longest timber viaduct in Wales and one of the oldest in regular use in Britain.
Barmouth is a seaside town and community in the county of Gwynedd, northwestern Wales, lying on the estuary of the Afon Mawddach and Cardigan Bay. Located in the historic county of Merionethshire, the Welsh form of the name is derived from aber and the river's name, "Mawddach".