The actress, who found fame playing Hermione Granger in the Harry Potter films, logged into the official Emma Watson Instagram account before uploading a racy pic.
The sultry black and white snap shows a woman in nothing but her birthday suit covering her most intimate region with some wallpaper.
However, despite the arty shot being shared on Emma’s official account, the lady in the picture isn’t actually Emma.
Instead, it is a snap by American artist and photographer Francesca Woodman.
Despite the reality of the pic, many fans initially thought it was their idol.
“Oh Merlin, I thought it was Emma,” one follower replied.
Another added: “You had me going there.”
“For a second I thought that was actually Emma Watson!” a third continued.
Last year Emma was forced to speak out after posing topless for Vanity Fair.
Lashing out during a promo tour for Disney’s live adaptation of Beauty and the Beast, Emma fumed: “Feminism is about giving women choice.
“Feminism is not a stick with which to beat other women with.
“It’s about freedom, it’s about liberation, it’s about equality.
“I really don’t know what my t**s have to do with it.”
Emma added to the BBC: “It’s very confusing. I’m always just quietly stunned.”