The sisters will appear in Olympic-themed ads this summer as well as in spots with Ronald McDonald, and their faces will appear on packaging in the US and on the McDonald's website, which encourages people to exercise more and eat a balanced diet.
Venus Williams has also signed a deal with the fast-food giant to design an accessory for the McDonald's Olympic Champion Crew, a selection of the best-of-the-best McDonald's staff from around the world, who will compete in a Big Mac building event in Athens.
Dean Barrett, senior vice-president at McDonald's, said: "Partnering with Venus and Serena Williams is about keeping our promise to McDonald's customers -- to work with the world's leaders in sports, music, fashion and entertainment and encourage people around the globe to incorporate physical fitness into their daily lives."
Between them, the sisters have won 16 Grand Slam titles. They are the first sisters to ever win the doubles event at the Olympics, the first sisters to win a Grand Slam title in singles and doubles play, and the first sisters to have ever met each other in a Grand Slam final. Venus and Serena will compete at the Olympics in Athens, playing for the US in singles and doubles competition.
"To star in McDonald's Olympic commercials and packaging is really fun and exciting for Venus and me. We grew up eating McDonald's and never dreamed back then we'd ever see ourselves in their commercials and on their packaging," Serena said.
McDonald's has also signed the basketballer Yao Ming to appear on the Go Active website, along with singer Justin Timberlake, who reveals that he keeps fit with a mix of calisthenics and free weights, and contributes his recipe for pasta primavera.
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