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Jennifer Hudson brings Down House at Jamie Foxx Birthday

TMZ <--Video

Jamie Foxx may have been the guest of honor at his 48th birthday party ... but it was Jennifer Hudson who stole the show.

We're told Jamie's friends threw a surprise bash for him at Le Bilboquet in NYC Saturday night -- and of course, there was major star power, including Alicia Keys and rumored GF Katie Holmes.

But it was his "Dreamgirls" costar, Jennifer Hudson, belting out, "And I Am Telling You," that was the best moment of the party.

Check out the video ... it's safe to say J Hud slayed.