Alix Earle and Stassie Karanikolaou Strip Down to Skimpy Bikinis on Italian Vacay

Alix Earle and Stassie Karanikolaou will eventually be coming back from Italy with some impressive tans ... because the two stripped down to catch some rays on vacay ... and we've got the sexy photos.

The pair were spotted hanging out off the coast of Sardinia on Tuesday ... with Alix wearing a skimpy black bikini ... and revealing almost all of her jaw-dropping booty.

Alix seemed to be getting in and out of the crystal-clear ocean throughout the day ... letting her wet hair hang down her back while also glistening underneath the hot European sun.

While Alix went with the simple all-black bikini, Stassie added a flash of color with a bright red number. Stassie's been hanging out with Alix in Europe this past week -- skipping her close pal Kylie Jenner's birthday bash amid speculation the pair aren't on good terms.

Zack Bia -- who used to be in a relationship with the recently engaged Madison Beer -- also hung out on the yacht ... and seemingly got handsy while rubbing Alix's lower back.

Alix has really been enjoying herself on this trip ... we've seen her on a jet ski, getting cheeky in Ibiza and flashing her cleavage in several form-fitting dresses.

Summer might be coming to an end ... but these smoking hot pics are going to live on forever!