The Sirhowy Tramroad was a plateway built to convey the products of ironworks at Tredegar to Newport, South Wales. It opened in 1805 between Tredegar and Nine Mile Point, a location west of Risca, from where the Monmouthshire Canal Company operated a tramroad to Newport. The Sirhowy Tramroad was operated at first by horse traction, but early locomotives were used, and a passenger service was operated.
In 1860 the Sirhowy Railway was incorporated to modernise the tramroad; it followed a similar alignment but with several modifications, and opened in 1863, between Tredegar and Nine Mile Point. A short extension northward to Nantybwch, joining the Merthyr, Tredegar and Abergavenny Railway, was opened shortly afterwards. The Sirhowy Railway was acquired by the London and North Western Railway, for which it formed a useful route to access Newport Docks.
The dominant traffic on the line was minerals: at first iron ore and later coal; the Great Western Railway used the lower part of the line for the trunk haulage of coal from Aberdare.
With the decline of the traditional mineral industries and the loss of local general traffic, the line closed in 1960.