The 29-year-old lock, who graduated from the Quins academy in 2005, will join the Top 14 club on a two-year deal as a replacement for Thibault Lassalle, who will join reigning European and Top 14 champions Toulon in the summer.
The only English club I have ever wanted to play for is Harlequins. It is a fantastic club where I have made many great friends and memories.
Oyannax, who won promotion to the Top 14 in 2013, have already began their recruitment for 2015-16 with announcements of Romania international prop Horaţiu Pungea from Lyon and former Wales international outside-half Nicky Robinson from Bristol heading to the Stade Charles-Mathon.
Robson has almost 200 club appearances to his name, which includes 138 in the Premiership and 45 in European competitions, but having spent nine seasons at The Stoop he is now ready for a new challenge abroad.
“I am extremely proud to have played a part in the success achieved by Harlequins in recent seasons and the memory of walking across the road and playing in the Premiership final in 2012 is something that will live with me and the supporters forever,” Robson said.
“However I have decided that the time is now right for me and my family to challenge myself in a different environment and culture.
“The only English club I have ever wanted to play for is Harlequins. It is a fantastic club where I have made many great friends and memories.
“I will now continue to put all of my efforts into helping Quins achieve our potential for the rest of the season.”
Robson was an integral part of the Harlequins side which won the European Challenge Cup in 2011 and the Premiership title in 2012 at Twickenham.
He goes with our best wishes; we will miss him hugely, not only on the pitch but also off it.
Despite not making a senior international appearance for England, he represented the Red Rose at age-grade level, played for the England Saxons, and captained the England senior side in the uncapped midweek side on their 2012 summer tour of South Africa.
Conor O’Shea, Harlequins director of rugby, paid tribute to Robson as one of the club’s great servants.
“We sat down last summer and George said he wanted to consider where he was before making any further commitments,” O’Shea said.
“On consideration George told me he was looking to experience something different and a few years in France for himself and his wife was an opportunity too good for them to turn down.
“He goes with our best wishes; we will miss him hugely, not only on the pitch but also off it.”
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