Supermodel Irina Shayk -- NUDE and Spotted ... for Your Pleasure

Let's put it this way..... someone should replace that dog Mona Lisa with Irina Shayk's most recent nude photo shoot ... it would definitely boost ticket sales at the Louvre.

The photo (ink tragically included) adorns a new coffee table book commissioned by Diddy and Interscope chairman Jimmy Iovine -- featuring lots of hot chicks from all over the planet -- to honor the female butt.

It's called "CULO" -- Spanish and Italian for ass -- and it's out next month.