England number eight Sam Simmonds will leave Exeter at the end of the season and join French Top14 team Montpellier.
Simmonds, 27, progressed through the Chiefs' academy and made his senior debut in 2012, scoring 80 tries in 117 appearances so far.
He has won two Premiership titles and a Champions Cup with Exeter, and been capped 14 times by England and once by the British and Irish Lions.
"It is a fantastic move for Sam and his family," said head coach Ali Hepher.
He added to BT Sport: "We have improved him as a player and he has done a fantastic job for us over the years. He has been a great player and he moves on to a cracking opportunity.
"As a player, you have to take certain opportunities that come your way, simply because you're not long in the game.
"That said, he's still a very important piece in the jigsaw that is here now and I'm sure Sam will have his say over the season and we get another quality year out of him, just like we have in the past."
England boss Eddie Jones expects Simmonds to be available for next autumn's World Cup, but once that is over his move to France will mean he is ineligible to play for the national side.
Saracens director of rugby Mark McCall said Simmonds' departure was worrying for the Premiership.
"Sam is 27, nearing his peak and is now making himself ineligible for England," said McCall.
"I kind of understand someone who is early 30s doing it after they've had their international career and want to experience something different.
"But to start losing the best young talent in the Premiership, someone like Sam, is a worry."