Which London Underground line is the network’s longest by route length?

The Central line is the longest London Underground line by route length.

It runs broadly east–west across London, linking West Ruislip and Ealing Broadway in the west with Epping and Hainault in the east. Its route is about 74 kilometres long, although the exact figure can vary depending on whether different branches or operational measurements are counted.

The line began as the Central London Railway, which opened between Shepherd’s Bush and Bank in 1900. It was later extended in both directions and absorbed into the London Underground system. Its distinctive map colour is red, while its trains are formed from 1992 Stock.

The Metropolitan line can seem like the obvious answer because it reaches far beyond central London into Buckinghamshire. However, “longest” generally refers to the complete route length of the Central line, including its western and eastern branches. The Northern line is more complex operationally, but it is not the longest.