By Len Brown
3:30 PM PDT, July 8, 2011
The Grammy-winning singer is set to hit 40 on December 24.
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Ricky Martin
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The Grammy-winning singer is set to hit 40 on December 24.
Winona Ryder
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The 'Black Swan' star will be celebrating her 40th birthday on October 29.
Snoop Dogg
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The West Coast rapper will reach the big 4-0 on October 20.
Sacha Baron Cohen
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The funnyman behind 'Borat', 'Ali G' and 'Bruno' is turning 40 this year on October 13.
Luke Wilson
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Owen Wilson's little brother will celebrate his 40th birthday on September 21.
Brooke Burke
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The "Dancing with the Stars" co-host turns 40 years young on September 8.
Lance Armstrong
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The 7-time Tour de France winner will hopefully be able to relax and enjoy his 40th birthday on September 18.
Amy Poehler
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The "Parks and Recreation" star will turn 40 on September 16.
Mark Wahlberg
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'The Fighter' star celebrated his milestone birthday on June 5.
Shannen Doherty
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The "Charmed" and "90210" star was excited to celebrate her 40th on April 12.
Ewan McGregor
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The 'Star Wars' actor turned 40 on March 31.
Denise Richards
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Charlie Sheen's ex spent her big day at Asselina restaurant on February 17.
Kid Rock
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The eccentric rocker celebrated his 40th birthday in his hometown of Detroit on January 15.
Mary J. Blige
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The R&B diva celebrated her 40th birthday surrounded by family and friends in New York City on January 11
Taye Diggs
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The "Private Practice" star jumped over the hill on January 2.
Stars Turning 40 in 2011
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The big 4-0. A milestone we all must reach, whether we like it or not, even for our favorite celebrities. Check out these pics to see who's turning, and who've already turned, 40 in 2011!