Bieber cheers on Mayweather in Las Vegas

By Lorena Blas, USA TODAY

Posted May 6, 2012

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Justin Bieber, Rapper Lil Wayne, boxer Floyd Mayweather Jr. and rapper Curtis '50 Cent' Jackson celebrate Mayweather's victory over Miguel Cotto by unanimous decision in their WBA super welterweight title fight at the MGM Grand Garden Arena on Saturday in Las Vegas. (Credit: By Al Bello, Getty Images)

Some stars celebrated Cinco de Mayo at the Kentucky Derby, but others celebrated at another major sporting event, the boxing match between Floyd Mayweather Jr. and Miguel Cotto.

Among the celebs ringside at the bout which took place at the MGM Grand in Las Vegas: Justin Bieber. That's right. The Biebs is a boxing fan and was there along with Lil Wayne and 50 Cent cheering on Mayweather. Their fighter won.

Bieber event sent a shout out about the victory to his Twitter followers: "@FloydMayweather Hard Work & Dedication. congrats champ. glad i could be a part of it"

But the pop singer called it a night quickly thereafter with a subsequent update: "in and out of vegas for the fight. now back for rehearsals tomorrow. goodnight world. hard work and dedication."