Richie Gray will be turning out for Toulouse next season after agreeing terms on a four-year contract.
The Scotland lock, 26, will move from Castres, a club he joined from Sale in 2013 after beginning his club career for Glasgow.
He said: ” This was a very difficult decision to make, I have loved my time in Castres, the club and the supporters have made my time here very special and I will leave with very fond memories.
“However the opportunity to play for one of Europe's most successful clubs, steeped in history, is an incredible one for me. When I met with the club they described their ambition and I felt this was the right move for me, to challenge myself in what is a very strong squad.
“I still have seven months here at Castres, I will give everything I can to the club in hope of achieving top six and then who knows.
“My goal for now is to leave Castres on the best possible note, I will give everything I can to the club, the players and the coaches”
