's tummy is looking tighter than ever -- just two months after giving birth!

The hot mama, who gave birth to daughter Blue Ivy on January 7, stepped out to an Obama fundraiser last night in New York City.

The 30-year-old singer looked amazing in a skin-tight blue dress from Victoria Beckham's collection. She paired the look with Lanvin jewelry and Nicholas Kirkwood shoes.

Beyonce has clearly been hitting the gym since giving birth -- and that should come as no surprise, since she's already scheduled her first post-pregnancy concerts for the end of May.

While her weight loss seems unbelievable, she's not alone.

Check out more stars who lost weight and got back into pre-pregnancy shape shortly after giving birth in the gallery above.

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