England back row forward Zach Mercer is leaving Bath to join French side Montpellier in the Top 14 next season, the English club announced on Monday.
In a statement on their website, Bath also revealed that 23-year-old Mercer will be replaced by South African Jaco Coetzee.
"It has been a long-standing dream of mine to play in France - the game is physical and will suit my playing style," said Mercer, a Bath academy product who is out of contract in the summer.
"I feel like I am able to offer the Top 14 something different and that is what I am looking forward to.
"I found it impossible to say no to the offer of a long-term contract with Montpellier."
Mercer, who has two England caps, made his international debut as a replacement for flanker Tom Curry in the 12-11 win over South Africa at Twickenham in November 2018.
His only England start came two weeks later at number eight in the 35-15 win over Japan, also at Twickenham.
Montpellier are second from bottom in the Top 14 and have lost their last seven matches.
Taking his place at Bath will be 24-year-old Coetzee, a powerful number eight, who plays for Western Province.
"With Jaco's arrival, we feel we have an unbelievably exciting addition to the squad," said Stuart Hooper, Bath's director of rugby.
"He's an intimidating ball carrier and will cause huge problems for our opposition no matter where he is on the field."
Bath are tenth in the 12-team English Premiership.