The VW subsidiary now sponsors three world-class soccer teams. The other two are Germany's FC Bayern and Spain's Real Madrid.
Audi will supply Manchester United with 20 cars over the current season and next season.
The club's soccer stars will also be invited to take part in driver safety training.
"We are proud to be working together with the world's most famous soccer club," said Gary Savage, Audi's UK marketing boss.
Manchester United's David Gill also praised the new partnership.
"Audi has the same level of brand value as Vodafone, Nike, Fuji, Budweiser and Pepsi," said Gill.
The sponsorship deal is Manchester United's first alliance with an automaker.
Audi boss Martin Winterkorn is a huge soccer fan. Winterkorn announced Audi's cooperation with FC Bayern in April 2002.
The partnership with Real Madrid started a year later.