The British team consists of 1,200 athletes from 47 sports
Visa is to sponsor Team 2012, the 1,200 British athletes training to participate in the London Olympics, the British Olympic Association has said.
The multi-million pound deal with the US credit card giant will provide funds to help the Olympic and Paralympic hopefuls continue their preparation.
The association said it was the largest national team to gain sponsorship.
Lord Coe, chairman of the organising committee for the London games, said it would help bring dreams to realty.
There had been reports of some initial opposition to the deal from leading athletes over image rights.
The London Olympics organising committee declined to comment.
The Press Association had reported that UK Sport reached an agreement with the athletes after promising that no fewer than four individuals - from a minimum of three sports - would be used in any images to promote Team 2012 or their sponsor.
Team 2012 is a joint project involving the British Olympic Association, UK Sport and the organising committee of the London Olympics.