Newcastle could earn £10million from the deal.
The new bank will become the club's main sponsor at the start of next season under an agreement which will run until the end of the 2013-14 campaign.
It will succeed Northern Rock's existing deal, which expires at the end of this season.
Newcastle managing director Derek Llambias: "We are naturally absolutely delighted to have signed a new deal with Northern Rock plc and to have their logo adorn one of the most famous and iconic jerseys in world football from the start of the 2010-11 season.
"This alliance underpins the desire of two of the region's most well-known names to continue to work together over the next four years.
"Sponsorship of Newcastle United is a proven commercial investment that not only generates significant media value for Northern Rock plc, but also enables the bank to connect to customers at a local and national level.
"Newcastle United's aim is to return to the Premier League next season and we believe that collaboration will help both companies achieve our respective goals in the local, national and international market place."
sponsorship deal with Newcastle United provides both of these."