The Waterloo & City line is a tube line operated by London Underground. Crossing under the Thames, it runs between Waterloo and Bank stations with no intermediate stops. Its primary traffic is bringing commuters from south-western England arriving into Waterloo mainline station to the City of London. As a primarily commuter link it does not operate on Sundays or public holidays.

It was opened on 11 July 1898, having been built by the Waterloo & City Railway Company. Bank station was originally named "City". It was the second electric tube railway to open in London, after the City and South London Railway (now part of the Northern line). Owned and operated by two mainline rail companies before nationalisation into British Rail, it was transferred to London Underground in 1994 following a major refurbishment and stock replacement. Entirely underground aside from a shaft at its Waterloo depot, the line is not connected to any other rail route; rolling stock is removed for refurbishment using a road crane.