The Surrey Iron Railway (SIR) was a horse-drawn plateway that linked Wandsworth and Croydon via Mitcham, all then in Surrey but now suburbs of south London, in England. It was established by Act of Parliament in 1801, and opened partly in 1802 and partly in 1803. It was a toll railway on which carriers used horse traction. The chief goods transported were coal, building materials, lime, manure, corn and seeds. The first 8+1⁄4 miles (13.3 km) to Croydon opened on 26 July 1803, with a branch line off from Mitcham to Hackbridge.

The Croydon, Merstham and Godstone Railway was built as an extension of the railway but by a separate company. It opened in 1805 and closed in 1838.The Surrey Iron Railway was commercially successful only briefly, until shortly after the opening of the canal between Croydon and London in 1809. It closed in 1846.