2:36 PM PT -- Kobe has ... (ahem) ... weighed in on the pics -- saying, "Objects on camera may appear larger than they do in the mirror haha."

He added, "ok...ok...ok. Gimme 30 days #challengeaccepted #mambathick #mambabeast."

Kobe Bryant's chest is just like his jumper ... SMOOTH!

The Mamba ditched the shirt for a relaxing poolside session in Portofino, Italy while on vacation with his family -- but just like the rest of us, he couldn't muster up the strength to put his phone away.

Italy is like a second home for Kobe -- he grew up there while his father played pro ball in Calabria and speaks fluent Italian.

Portofino is poppin' right now for rich people -- Kris Jenner hit up the vacation spot last month. Same with Tiffany Trump. And Heidi Klum was there last week!

Maybe they all use the same waxer?