From 1 July, Carrington will be known as the 'AON Training Complex' as part of the eight-year agreement with the club's present shirt sponsors.
The deal also includes sponsorship of United's training kit, their annual summer tours and, for the first time, friendly matches.
As had already been agreed, AON will also become the principle partner of the Manchester United Business Network and also sponsor of the Manchester United Foundation.
The deal highlights the commercial value of United, who have also signed a £357m, seven-year deal with US car company General Motors to have its Chevrolet name on their shirts from 2014, when the AON agreement expires.
An AON source said the company were delighted with the training ground deal.
"We are very aware and respectful of the fact some people will continue to call the training complex Carrington but in time, we hope they come to understand what the AON brand stands for," said the source.
"But we feel this agreement will enable us to do something with the club which is unique. We have been more than delighted by our partnership with Manchester United."
The deal has prompted suggestions that United could also sell naming rights to their Old Trafford ground, but this has been quickly dismissed by the club.
"Old Trafford will not be sold," said Ed Woodward, United's executive vice-chairman, who will replace David Gill as chief executive in the summer.