Wales fly-half Rhys Priestland will join Bath when his deal with Scarlets expires at the end of the season.
Priestland will switch to the Premiership after this summer's World Cup, bringing to an end his 10-year association with the Pro12 club.
The 27-year-old will compete for a first-team place at Bath with England number 10 George Ford.
Priestland has made 147 appearances for Scarlets, scoring 1,059 points, and also has 32 caps for his country.
|Analysis: Ex-Bath centre Jeremy Guscott|
|"It's a brave move. He's 27, George Ford is pretty established not just in the Bath side, but also getting there as far as England is concerned. Rhys has a world-class game in him. When he's on form and when he's confident, he can dictate the tempo and direction of the game.If I was a player of his calibre, Bath would not be the club I would join."|
But his move to England could affect his international prospects, as a new selection policy means players leaving Wales could be excluded from Warren Gatland's team unless there are exceptional circumstances.
The policy will become active once a minimum of six senior players, prioritised by Gatland, have been signed to national dual contracts.
However, Priestland's absence from Wales would benefit Bath, with Ford now a regular for England.
"My entire rugby career has been spent in Wales and, although I've enjoyed that time enormously, I need a new challenge," said Priestland.
Speaking about competition for the number 10 shirt at Bath, coach Toby Booth told BBC Radio Bristol: "We believe that having Rhys here means he and George can push each other along.
"They'll allow each other to get the best out of each other and, ultimately, drive the team forward.
"Rhys is coming here on the proviso he is the first-choice 10. He's happy to fight it out."