Believe it or not, the 'man in the iron mask' above is none other than mega-movie star Leonardo DiCaprio. And what makes this pic so odd is that Leo's not even working on a movie!

No sir, the camera's aren't rolling and he's not in costume. In fact, the 'Great Gatsby' star was recently photographed in disguise while walking the streets of Venice, Italy where he's currently on vacation.

Stranger still, DiCaprio wore sunglasses, met with friends and stopped for pizza -- mask on all the while!