Wales scrum-half Mike Phillips has finalised his move to French side Bayonne on a two-year contract.
The 28-year-old had a contract with the Ospreys until 2012, but fell out of favour following the Six Nations and was told he could find a new club.
Although Phillips has signed a two-year deal he has the option of a third year.
The 2009 British and Irish Lions scrum-half in South Africa will join up with Bayonne after the conclusion of Wales' World Cup campaign.
Phillips is one of a number of new recruits at big-spending Bayonne, who have also signed Test stars such as France wing Cédric Heymans, Australia lock Mark Chisholm and New Zealand trio Joe Rokocoko, Sione Lauaki and Neemia Tialata.
Bayonne finished eighth in the French Top 14 last season and the Basque side had courted All Blacks number nine Byron Kelleher after the campaign, only for contract negotiations to break down over his proposed move from Toulouse.
Phillips is the third Ospreys player to exit the Welsh region for a French club, with full-back Lee Byrne and fly-half or centre James Hook having signed for Clermont Auvergne and Perpignan respectively.
Ospreys boss Scott Johnson said in April they were prepared to let the former Scarlets and Cardiff Blues player leave.
"After continued requests from Mike over the last 18 months, we've agreed to let Mike go as soon as he can find another club," Johnson said at the time.
"I think it gets to a stage where within an organisation, anyone who doesn't want to be here will move on."
Wrexham-based rugby league side Crusaders confirmed they had approached Phillips over a possible move to the Super League side, but he has opted to remain in rugby union.
Phillips's opportunities at the Ospreys were limited since the Six Nations Championship and he fell behind youngster Rhys Webb in the pecking order.
The Ospreys have signed Samoan international number nine Kahn Fotuali'i from Super Rugby team the Crusaders for next season.
Phillips started for Wales against the Barbarians at the Millennium Stadium on 4 June to win his 52nd cap and has been included in a 45-man preliminary World Cup squad.