Joel Embiid says he's OVER Rihanna -- officially declaring he's moving on after trying to get a date with her for years.
Seems Lakers rookie Josh Hart thinks Embiid's making a mistake.
Backstory ... Embiid has long claimed he hit on Rihanna back in the day and she told him to come back when he made the NBA All-Star team.
Well, now he has ... he'll be a starter on the East ... so, TNT's Kristen Ledlow asked Joel if he had a message for RiRi now.