Scott Disick and Sofia Richie Kiss in Miami Beach

Scott Disick's moved on to his next fling, but he's keeping things consistent -- she's another hot young celeb still in her teens.

Scott and 19-year-old Sofia Richie chilled on the beach in Miami Thursday after arriving together earlier in the day for an apparent couples vacay. The 2 soaked up some sun ... and shared a kiss by their waterfront hotel.

We've seen them hanging out around L.A. for weeks now, but there's never been any PDA. These Miami pics make it clear Scott's found the perfect follow-up to also 19-year-old Bella Thorne -- who he was dating over the summer.

Well played, sir.