The Southwold Railway was a British 3ft Narrow Gauge Railway. 
Built in 1879 and closed in 1929.
The main line was 8 miles (14.15 km) long, running from Southwold to Halesworth, stopping at three intermediate stations, Walberswick, Blythburgh and Wenhaston.
The was a link to Blackshore Quay, between Southwold and Walberswick, which was to be 0.25 miles long.

The railway had with three locomotives for the opening, but a total of four by closure, built by Sharp, Stewart Company.
They had a 2-4-0/2-4-2 wheel arrangement, and the design was similar to others that the company had supplied for light passenger work. 
Sharp Stewart also supplied rolling stock.
Construction of the railway had cost £90,000, (equivalent to £9,220,000 in 2020).
A maximum speed of 16 miles per hour (26 km/h) was specified, and it was worked by one engine in steam.

At Halesworth, the single platform had a shelter for the passengers, and was connected to the Great Eastern Mainline station by a footbridge. There was a raised timber platform between one of the sidings and a standard gauge siding, where goods were transhipped. 
Many of the trains were mixed goods and passenger workings, with the shunting at intermediate stations adding to the journey time for the passengers. 
The stock did not have a continuous brake, and although the Board of Trade raised the issue at regular intervals, the railway was always able to point to its clean record for transporting passengers, and somehow managed to avoid having to fit one.

In 1906 it was announced that the line would be widened from its present narrow gauge to allow carriages and wagons to come direct through from Halesworth. This was not carried out, and sadly the railway closed on 11 April 1929.

After that the Railway lay dormant for a number of years, until the outbreak of World War Two, when the remnants of the Railway were broken up for scrap to help aid the war effort.