Southampton have completed the signing of Stuart Armstrong from Celtic for a fee of £6m.

The 26-year-old has agreed a four-year contract with the Premier League club and will link up with his new team-mates on Thursday for the start of pre-season.

Armstrong established himself as a major creative force in midfield during his three-and-a-half years with Celtic, netting 17 goals during the 2016/17 campaign, as he helped the Glasgow giants to an unbeaten season and the first of back-to-back domestic trebles.

The Scotland international, who began his career with Dundee United before joining Celtic in 2015, chose to move to St Mary’s amid interest from other Premier League sides, becoming the first addition of the summer to Mark Hughes’s squad.

Armstrong said: “Southampton seems a really good fit for me. Watching from afar, I really enjoy the attractive football that they play and I’m very happy to be here.

"Every season, I put demands on myself to create and score goals. I hope going forwards from here that it will be the same this term at St Mary’s.

"I’m looking forward to meeting everyone and I’m very excited to get started. It’s a four-year contract; there will be a lot to learn and I want to hit the ground running."

Hughes said: “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.

“We have strong players in the squad and it is important we build on that by adding different qualities. 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.

“He brings with him extensive experience of European football and has developed his game impressively over the past few seasons at a major club in Celtic, where there is a demand not only to perform but also to win. Stuart has done both during his time there.

“Our research tells us he is an excellent young man, intelligent, and a strong team player, and clearly having another really good character in our group is part of what we want here at Southampton.

“He has shown tremendous drive to improve and has also displayed a great desire to be a part of what we are trying to achieve here, and I believe he will be a real asset to the squad in the years ahead.”