Fly-half Alex King has signed a one-year deal to switch from Wasps to Clermont Auvergne in the French Top 14.
King helped Wasps to the Heineken Cup title in May
The 32-year-old, whose Wasps contract had expired, has an option for a further year but could also return to the Londoners as a coach.
King has won five England caps and spent the last 11 seasons with Wasps.
"Clermont is a very ambitious club," said King. "It's important for me to go to a team that is motivated because I still have lots to learn and to give."
It has been a fantastic 11 years, but hopefully I will be back at Wasps one day
King, who was instrumental in Wasps' Heineken Cup triumph in May, added: "The end of last season wasn't quite the right time to decide what I was going to do.
"I wanted to be able to focus purely on preparing for the Heineken Cup final and after that was over, obviously things were then very emotional.
"The victory at Twickenham was a great day in the history of the club, and one that is very special to me, one that I am proud to have been a part of.
"When the offer came in from France I could see that it would be a fantastic opportunity to gain some new experiences.
"Having said that, it was a massively difficult decision to make. I've had some of the best times a rugby player could hope for at this club, and made some fantastic and hopefully lifelong friendships with some truly special people.
We have plans to develop a coaching position for him at Wasps when he reaches the end of his playing days
"However, I thought long and hard about the decision, and I do believe this is the best thing for me and my family.
"It has been a fantastic 11 years, but hopefully I will be back at Wasps one day."
Wasps director of rugby Ian McGeechan said: "Alex has been core to everything Wasps has been about in recent years and I hope he will continue to be so in the future, as we have spent some time discussing his options once he has retired from playing.
"I believe he will continue to be a very important part of the club in the future, and to that end we have plans to develop a coaching position for him at Wasps when he reaches the end of his playing days."
King, who will be joined at Clermont by South Africa captain John Smith and fellow Springbok Maruis Joubert, will face his old club in the Heineken Cup next season.
King joined Wasps in July 1996 and played a major part in their victorious league campaign that same season.
During his time at the club, Wasps also won three straight Premiership titles between 2003-5 as well as the Heineken Cup in 2004 and four other cup titles.
Clermont beat Bath to win the second tier European Challenge Cup final at Twickenham in May but lost to Stade Francais in France's Top 14 final.