British Rail Class 319 dual-voltage electric multiple units (EMU) were built by BREL York in two batches from 1987–88 and 1990. The trains were introduced for new north-south cross- London services from Bedford to Brighton, and since privatisation these services have been operated by Thameslink and First Capital Connect, the former franchise having been merged with the Great Northern section of the former WAGN franchise to form the latter train operating company at 0200 BST on 1 April 2006 as a result of re-franchising. Class 319 units have dual power pick-up, from either 25 kV alternating current (AC) overhead lines for services north of London, or 750 V direct current (DC) third rail to the south. However, some units were only used on outer suburban services in South London. The Class 325 postal units were based on the Class 319 units, with the same traction equipment and body design, but are fitted with cabs of the same design as the newer Class 365 and Class 465 Networker units.
Since delivery of new rolling stock for Thameslink services commenced in 2015, a number of Class 319 units have been redeployed for use on other operators' services, including in the North West of England.