The Wirral Line is an underground railway service operating in which UK county?

The Wirral line is one of two commuter railway lines operated by Merseyrail and centred on Merseyside, England, the other being the Northern line. A third line of the Merseyrail network, the City Line, is not operated by the Merseyrail train operating company, though it also receives funding from Merseytravel, the passenger transport executive for Merseyside.

The Wirral line connects Liverpool to the Wirral Peninsula via the Mersey Railway Tunnel, with branches to New Brighton, West Kirby, Chester and Ellesmere Port. Beneath Liverpool, the line follows a clockwise circular route in a single-track tunnel called the Loop, built in the early 1970s.

The line was created by the amalgamation of several historic railways, and has carried its present name since the opening of the Merseyrail network by Queen Elizabeth II on 25 October 1978 during the British Rail period. The Wirral line is fully electrified with a DC third rail, and has existed in its current form since May 1994 with the start of electric services to Ellesmere Port. A total of 34 stations are served, with connections available to mainline services at Liverpool Lime Street and Chester.