Wales second-row Luke Charteris is set to join Bath from Racing 92 on a three-year contract.
Charteris left Newport Gwent Dragons for Perpignan in 2012 and then signed for Racing 92 in 2014.
The 62-cap, 6ft 9in player is out of contract at the end of the 2015-16 season and would then join the Premiership club.
Gloucester had also held discussions with the 32-year-old, while the Dragons had hoped to re-sign him.
Racing and Wales scrum-half Mike Phillips believes Charteris' departure would be a blow for the French club.
"If we do lose his talents then obviously it is a massive loss. He is one of Wales' best players at the moment," he said.
"There are not many 6ft 9in guys who can make as many tackles as he makes - 18 or 20 tackles [a game].
"He carries balls, he scrummages well, he can do everything on the rugby field and is such an athlete."
Newport Gwent Dragons coach Kingsley Jones said they would like to re-sign Charteris, but feared they would be outbid by English and French clubs.
Bath already have a Wales lock in their squad. Dominic Day joined the club in 2012 and signed a contract extension with them in January 2015.
In October, last season's Premiership runners-up missed out on the signing of Dragons back-row forward Taulupe Faletau after Wales coach Warren Gatland blocked the move.
Wales fly-half Rhys Priestland is also at Bath and concentrating on his club career during a sabbatical from Test rugby.