The Mablethorpe Loop railway was formed in Lincolnshire, England, by two independent railway companies, which built branches from the East Lincolnshire Line.
The Louth and East Coast Railway opened its line, approaching Mablethorpe from the North, in 1877. This was followed by the opening of the Sutton and Willoughby Railway and Dock company in 1886; it had planned to create a large fishing dock at Sutton le Marsh, but it was unable to generate the capital to do so. Abandoning the dock idea, instead it built a connecting line to Mablethorpe, approaching from the south, and opening in 1888. Together the lines formed a loop off the main line. The two small companies sold their concerns to the Great Northern Railway in 1902 (S&WR) and 1908 (L&ECR).
Mablethorpe developed very considerably as a holiday and excursion destination, facilitated by the railway connection, and the GNR did much to foster the business, running through excursions from Midlands towns, and later London, as well as handling holiday visitors. The local traffic was never significant, and the L&ECR section closed in 1960; as seaside holidays in Britain lost popularity, the remaining line declined and was closed in 1970.