Serco-Abellio is a joint venture between Serco and Transport UK Group, each owning 50%. The joint venture is the train operating company of the Merseyrail franchise since July 2003 in the Liverpool City Region. It previously operated the Northern Rail franchise in Northern England from December 2004 until March 2016.

Serco Group plc is a British multinational defence, health, space, justice, migration, customer services, and transport company. It is headquartered in Hook, Hart, England. The company operates in Continental Europe, the Middle East, the Asia Pacific region, including Australia and Hong Kong, and North America. It is listed on the London Stock Exchange and is a constituent of the FTSE 250 Index.