Stassie Karanikolaou's stepping out of Kylie Jenner's shadow and serving up some serious sun-kissed vibes in St. Barts ... alongside another smokin' hot pal, Justine Skye!

These pics are straight fire -- Stassie’s curves were on full display in a tiny black floral string bikini, rocking a trucker hat to shield herself from the scorching rays while cranking up the heat on her Caribbean getaway.

While her bestie may not draw the same fanfare as Kylie, Justine still knew how to command attention in a snakeskin print bikini as the pair splashed around in the sea.

The duo has been living their best vacay life for days, ringing in the New Year in style with other sizzling beach sightings.

Looks like Stassie and Justine are giving the Caribbean sun a run for its money!