Santander UK plc is a United Kingdom bank, wholly owned by the Spanish Santander Group. Santander UK plc manages its affairs autonomously, with its own local management team, responsible solely for its performance. Santander UK is one of the UK's leading personal financial services companies and one of the largest providers of mortgages and savings in the UK. The bank has circa 20,000 employees, 14 million active customers, with almost 1,010 branches and 50 corporate business centres.

The bank, with its head office in the London Borough of Camden, was established on 11 January 2010 when Abbey National plc was combined with the savings business and branches of Bradford & Bingley plc, and renamed Santander UK plc. Alliance & Leicester plc merged into the renamed business in May 2010.

Between 2007 and 2010, Santander was ranked as worst bank for customer service in the J. D. Power UK Retail Banking Satisfaction Study. However, its '123' product range was ranked third best in the UK in 2013 and in a moneysavingexpert.com poll in 2014 customers ranked their satisfaction higher than with any of other main high street banks.