Southampton have signed Scotland international Stuart Armstrong from Celtic on a four-year deal for a reported £7 million.
The midfielder was beset by injuries last season, one year after scoring 17 goals.
He is the Premier League club's first signing of the summer.
"Southampton seems a really good fit for me," Armstrong said in a statement. "Watching from afar, I really enjoy the attractive football that they play and I'm very happy to be here."
Southampton narrowly avoided relegation last season under Mark Hughes, who replaced Mauricio Pellegrino in March.
"Stuart is a player who we have admired for some time, and I am delighted we have been able to bring him here, especially given the competition we faced to sign him," Hughes said in the statement. " ... It is important we add a greater goal threat to the team as a whole, and to our midfield specifically, and Stuart's record of scoring and creating makes him an extremely exciting addition in that area."