With the Ospreys having now reached agreement with the French club, Byrne will be free to join the T14 side at the end of the current campaign after five years at the Liberty Stadium.
Ospreys Managing Director, Mike Cuddy, explained: "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 twelve 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."
Byrne signed for the Ospreys in the summer of 2006 from the Scarlets, marking his debut for the region with a try in the 17-11 win over Edinburgh at the Liberty Stadium on the opening weekend of the 06/07 campaign. In his time with the Ospreys he has established himself as first choice fullback for Wales, as well as representing the British & Irish Lions in South Africa, and to date has made 89 appearances for the region, scoring 27 tries.
Ospreys Elite Performance Director, Andrew Hore, added: "Lee has served the Ospreys well in his time with us, and has developed from a back three utility player into a highly accomplished fullback capable of competing at the top level. However, it is the nature of professional sport that players move on and teams evolve, which is why have reluctantly agreed to this deal with Clermont Auvergne to release Lee from his contract at the end of this season, a year early.
"Confirming the position at this early stage allows us to plan for next season with a degree of certainty, and to identify the key areas where we need to strengthen the squad with a view to 2011/12 and beyond."
Byrne commented: "I'll be sad to leave my home region but 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 for me in France, and the challenges that lie ahead for me.
"I'm extremely thankful to the Directors of the Ospreys for the way that they have handled this, allowing me to look ahead to what will be a fantastic experience for me. In the longer term, the Ospreys is my region, and I'd like to think that I will be able to return here before my career is over."