Back-rower Jac Morgan will be leaving the Scarlets at the end of the season.
A product of the Scarlets Academy, the 21-year-old has played 15 senior matches over the last two seasons, including four in European competition.
Scarlets offered Jac a new contract to remain at Parc y Scarlets, but he has opted to move on.
Scarlets general manager of rugby Jon Daniels said: “We are obviously disappointed that Jac has chosen to leave. He is one of a number of outstanding home-grown opensides we have here at the Scarlets, a young player who has come through our system, who has already captained our A team and taken his opportunities in the senior side this season.
“We wish Jac well for the next chapter in his career, but he still has a big part to play for the Scarlets in the PRO14, Champions Cup and Rainbow Cup this season.”
Jac, who has agreed a move to the Ospreys, said: “I am hugely grateful to the Scarlets for everything they have done for my development. There is a big few months ahead and I am looking forward to giving everything to help us finish the season on a high.”