The deal follows the news on Monday that Asda is to drop its long-running "Always low prices" slogan in a major revamp as it boost its marketing spend to £45m to match that of rival Tesco.
The brightest star of English football and his girlfriend are to front the struggling retailer's advertising for the next two-and-a-half years.
The deal will also see McLoughlin, best known for shopping, design clothes for Asda's George clothing label.
McLoughlin said: "I'm just in the learning stages at the moment. Victoria [Beckham]'s jeans are great but I'd like to do something different."
The deal comes ahead of the 2006 World Cup, in which England are seen as having a strong chance of winning, ensuring maximum exposure for the retailer, which is battling with rival Sainsbury's to hang on to the number two supermarket slot behind leader Tesco.
First up will be a "Summer of Sport" ad campaign. The pair replace Sharon Osbourne, the TV presenter and wife of Ozzy, who was dropped as the supermarket's spokeswoman in September after less than a year.
The signing of the Asda deal concludes a lucrative week for the striker, who is to pocket £5m in a 12-year, five-book deal with publisher HarperCollins.
It is understood that Asda beat out retail rivals to sign Rooney, who is likely to see his celebrity status soar during the World Cup.
The "Always low prices" slogan is being replaced by "More for you for less", and will first be seen in a new TV ad campaign this week created by the retailer's agency Publicis.
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