Pic Of Dead Body NOT Robin Williams

Someone has posted a pic of what they claim to be Robin Williams' body at the Coroner's Office ... but we've learned it is NOT Robin.

We've traced it back ... the pic was taken from a Spanish language website that deals with strangulation and has several images posted to illustrate. The image that was sent around Tuesday night resembles Robin, but it was posted several years ago.

Zelda Williams was extremely upset by the pic, tweeting, "I'm shaking. I can't. Please. Twitter requires a link and I won't open it. Don't either. Please."

Zelda then deleted her tweet and apologized, saying "I should've risen above."

Law enforcement confirms to TMZ ... the pic is NOT Robin's body.