Move over Marky Mark, there's a new CK hottie in the house!

Justin Bieber stripped down to his skivvies for the new Calvin Klein campaign, and either the set stylist stuffed his crotch, or The Biebs is seriously packing! Who knew?!

The Canadian crooner makes love to the camera shirtless with his tattoos on full display, and in another shot he cuddles up to model Lara Stone. All JB's time in the gym lately has certainly paid off!

We can see why Selena Gomez has a terminal case of Bieber Fever!