From face paint to studs, Ke$ha loves to change up her look.

But her latest one may be her most shocking -- she just posted a Twitpic without a stitch of makeup!

"No makeup Monday," the 26-year-old singer wrote underneath the photo ... which she posted on Wednesday.

It was a little odd, but nothing compared to the time she had sex with a ghost or drank her own pee.

Click on the "Launch Gallery" button above to see more stars without makeup and vote on which look you prefer, below.

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