Merseyrail is an urban rail network serving Liverpool, England, the surrounding Liverpool City Region, the Wirral Peninsula, and the adjacent areas of Cheshire and Lancashire. The core of the network is formed by two dedicated electrified lines known as the Northern Line and the Wirral Line, which serve underground stations in the centres of Liverpool and Birkenhead. Separate from the third rail electrified network is the City Line, which is a term used by the governing body Merseytravel referring to local Northern Trains services it sponsors serving in its area operating on the Liverpool to Manchester Lines and Liverpool to Wigan Line. Many of the City Line stations are branded Merseyrail using Merseyrail ticketing.

The Merseyrail third rail network has 68 stations and 75 miles of route, of which 6.5 miles are underground. Carrying approximately 110,000 passengers each weekday, or 34 million passengers per year, it is one of the most heavily used urban railway networks in the UK outside London.

The first part of the large comprehensive urban network was initially opened in 1977 by merging separate rail lines by constructing new tunnels under Liverpool city centre and Birkenhead. Although financial constraints have prevented some of the 1970s plans for the network from being realised, the network has been extended on its peripheries, with additional extensions proposed. The extensions were created by electrifying existing lines and then transferring the electrified sections into Merseyrail.

The network is operated by a joint venture between franchise holder Serco and Abellio, who superseded Arriva Trains Merseyside in 2003. The contract is for 25 years expiring in 2028. As of 2015, Serco-Abellio operates a fleet of 59 trains and employ 1,200 people.

Point-to-point or return tickets are purchased from staffed offices or ticket machines, but the system is tightly integrated with Merseytravel’s City Region-wide pass system, which also encompasses the Mersey Ferries and city and regional bus networks. Merseytravel’s smart ticketing is via the local MetroCard smartcard system, including Merseyrail travel.