Wales full-back Lee Byrne will join Clermont Auvergne on a three-year deal from the Ospreys.
Byrne had a year to run on his Ospreys deal but the region have accepted compensation from the French club.
"This was too good an opportunity for me to turn down at this stage of my career and I'm excited about what the future holds," said Byrne.
His move came less than a week after fellow Osprey James Hook confirmed a three-year deal with Perpignan.
Including Gavin Henson (Saracens), three British and Irish Lions will have left the Ospreys this season.
The Ospreys also tried to keep Henson on their books, but later indicated they would be open to offers for the 30-year-old.
Provided Byrne is named in Wales' squad for the 2011 World Cup, he will make his Clermont debut in the Top 14 after the tournament is over.
Ospreys managing director Mike Cuddy said: "First and foremost, the Ospreys are about developing local talent, and producing players not only for the region, but for the national team also.
"As such, it is extremely disappointing to lose a player who hails from the region, and who has been, and continues to be, an excellent servant to the Ospreys.
"Our determination to keep Lee at the Ospreys meant that we fought hard to keep him here, turning down a similar request 12 months ago.
"But unfortunately, the circumstances are such that we now find ourselves in this position where we have reluctantly agreed to release Lee, given his desire to take on a fresh challenge following the Rugby World Cup later this year.
"We would not have seen much of Lee next season, when he will be 31, and for him to have the security of a three-year contract and the change of lifestyle that this move will allow him is a fantastic personal opportunity and we wish him the best of luck. "
Although Byrne will be a loss, he has not been in his best form since returning from a broken thumb sustained playing for Wales in the autumn internationals and is set to lose the Wales number 15 jersey to Hook for the Six Nations opener against England on Friday, 4 February.
The Ospreys do have full-back cover. The experienced Barry Davies has worn the number 15 shirt in Byrne's absence, and Gareth Owen has been tipped as a potential star of the future while 18-year-old Welsh international Tom Prydie is also competing for the full-back role.
Byrne joined the Ospreys from close rivals Llanelli Scarlets in 2006 and signed a new four-year contract at the Liberty Stadium in 2008.