DMG Entertainment, a Chinese advertising agency, have signed Michael Phelps as brand spokesperson for Mazda in China following the swimmer's haul of eight gold medals during the 2008 Beijing Olympics.
The campaign will be unveiled later in the year, and will feature Phelps in newspaper, magazine and billboard adverts as well as television commercials.
"The people of China have been very supportive of me and my efforts to help promote swimming," said the swimmer.
"I am excited to begin 2009 with my first return trip to Beijing since the Games.”
DMG claim that the sponsorship is the largest single endorsement deal for a Western celebrity in China's history.
"This deal demonstrates the buoyancy of China's advertising economy," said Dan Mintz, DMG's chief executive.
"China is increasingly looking to elite personalities to endorse domestic and international brands.
"This is just the first of a number of high-profile partnerships that DMG Entertainment is negotiating that will open a new chapter in China's advertising industry."