The hitmaker was left exposed as she performed an energetic set after her skimpy costume struggled to contain her ample assets.
An eagle-eyed fan caught the unlucky 35-year-old's embarrassing moment on camera, when her boob popped out during a tricky dance move.
Britney was in a sparkly green leotard, complete with a dangerously low-cut neckline, when the mishap happened.
The mother-of-two's wardrobe malfunction reportedly came about after a dancer accidentally grabbed the wrong part of her outfit.
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Britney Spears suffered an epic wardrobe malfunction while on stage in Las Vegas
Britney's breast fell out of her leotard mid-performance
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Britney was singing Work B***h and strutting across the front of the stage when she revealed a little too much.
Proving she is ever the professional, the blonde beauty quickly covered up her nip slip and continued the set at Planet Hollywood.
"Britney's boob is OUT and she doesn't care," one person tweeted, while another user wrote: "Britney's boob popped out on stage I'm LIVING."
Britney regularly takes to the stage in an array of sizzling outfits
Britney Spears' sexiest performances
Mon, January 23, 2017
Britney Spears shows off her enviable curves in an array of revealing ensembles during her live shows.
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Britney Spears sends fans wild as she flashes the flesh in VERY revealing cut-out bodysuit
The American singer made her comeback last year, and has since blagged herself a new boyfriend in the form of 22-year-old model Sam Asghari.
Britney's humiliating show comes just hours after it emerged that a male fan had spent £60,000 to look like her.
Bryan Ray from Los Angeles started copying her at 17, when he had veneers, but has since had more than 90 cosmetic procedures including a nose job.