The Romney, Hythe & Dymchurch Railway is a 1 ft 3 in (381 mm) gauge light railway in Kent, England. The 13+1⁄2 miles (22 km) line runs from the Cinque Port of Hythe via Dymchurch, St. Mary's Bay, New Romney and Romney Sands to Dungeness, close to Dungeness nuclear power station and Dungeness lighthouse.
Constructed during the 1920s and opened on 16 July 1927, the Romney, Hythe & Dymchurch Railway was the dream of millionaire racing drivers Captain J.E.P. Howey and Count Louis Zborowski. Zborowski was killed in a motor racing accident at Monza before the Romney Marsh site was chosen, and Howey continued the project alone.
From 1926 to 1978, the RH&DR held the title of the "Smallest public railway in the world" (in terms of track gauge). The title was lost to the 12 1⁄4 in (311 mm) gauge Réseau Guerlédan in France in 1978 and regained from 1979, when the Réseau Guerlédan closed, until 1982, when the 10 1⁄4 in (260 mm) gauge Wells and Walsingham Light Railway opened.
The railway was featured in an episode of the BBC series The Inspector Lynley Mysteries.