The Southbury Loop is a line linking Edmonton Green, in north-east London, with Cheshunt. It was opened by the Great Eastern Railway in 1891. Initially, it was not very successful and was closed to passenger traffic in 1909. Goods trains continued to use the line and during World War I passenger services were reinstated for munitions workers. Once the war finished the line returned to its goods-only status although it was occasionally used for diversionary purposes when the West Anglia Main Line was closed south of Cheshunt. Electrification of the line and the reintroduction of passenger services in 1960 saw the line become busy with regular suburban services as part of the Lea Valley Lines network. Since May 2015 passenger services on the line have been part of London Overground.

The Lea Valley lines are two commuter lines and two branches in north-east London, so named because they run along the Lower Lea Valley of the River Lea. They were part of the Great Eastern Railway, now part of the Anglia Route of Network Rail.