Mariah Carey
is one hot mama! 

The singer posted a brand new bikini pic via Instagram on Monday  -- and she's showing off her famous physique in a tan two-piece swimsuit.  

"Working in my most favorite environment clearly having a bad hair day.. Haaaaaa," the 43-year-old captioned the sexy snap. 

We think the Mariah looks great (even with that hair) -- can you believe she's a mother-of-two? The "Butterfly" singer doesn't ever seem to age! 

How do you think Mimi looks? Tell toofab in the comment section below, and click "Launch Gallery" above to see even more celebrity beach bods!

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