Penallt Viaduct is a viaduct that formerly carried the Wye Valley Railway over the River Wye, which at this location forms the border between England (Gloucestershire) and Wales (Monmouthshire). The 14-mile Wye Valley Railway opened on 1 November 1876.
The viaduct is a single-track curved structure of five girder spans supported on four pairs of cast iron columns, located between Redbrook on Wye and Penallt Halt stations. Passenger services ceased on the railway in 1959, but the viaduct is still open to carry a public footpath over the Wye between the villages of Redbrook and Penallt.
Coordinates: 51°47′07″N 2°40′26″W / 51.78526°N 2.67382°W