The Cardiff Riverside Branch was a short railway constructed as an industrial railway in Cardiff, South Wales by the Great Western Railway. New industries had developed along the banks of the River Taff south from Cardiff Central station towards Cardiff Docks. Whilst the main Bute and Roath docks were well serviced well by both the GWR and the Taff Vale Railway, the relatively thin spit of land along the banks of the River Taff between the docks and the TVR's Penarth railway, known locally as "Rat Island", were not.