Former France lock Julien Pierre will leave Clermont at the end of the season to join likely Top 14 newcomers Pau.
The veteran second row has been at Clermont since 2010 when he arrived from Bourgoin, and established himself for France during that time.
The 33-year-old won a total of 27 international caps and was part of the French team that reached the World Cup final in 2011.
He will join Pau on a two-year deal from next season, and will almost certainly get the chance to go up against Clermont in his first season, with Pau currently 15 points clear at the top of Pro D2.
His signing is the latest in an ambitious recruitment drive from the club from the south west, with Conrad Smith having already announced his arrival from the Hurricanes.
Richie McCaw and Imanol Harinordoquy are among other players to have been linked to the club for next season.
Elsewhere Clermont could be set to lose another veteran leader, with Julien Bonnaire linked to a switch to Lyon at the end of the season.
The long-time French international is now 36 and is believed to be keen on a return to the south east of France and his family as he edges closer to retirement.