Southampton have completed the signing of defender Virgil van Dijk from Celtic.
The 24-year-old former Holland under-21 international has signed a five-year contract with Saints after a successful two years in Scotland.
A long-term target of Southampton, Van Dijk said the “unbelievable” opportunity to play in the Premier League was something he could not refuse.
“I’m delighted. It was a very easy decision to join this club,” he told Southampton’s official website.
“This is a very ambitious club, who have been doing very well in the last couple of years. It’s a great place to be and it’s the right step for me.
“For me now to get the opportunity to play in the Premier League is unbelievable and I will enjoy it. I know it’s an ambitious club – they have been through a lot throughout the years. They are trying to play football and that’s something that really attracted me.
“I’m so excited. I hope to settle in really quick, get everything around football sorted, start playing and enjoying it because the most important thing in football is to have fun and enjoy every day.”
Speaking to Celtic’s website, he added: “I would like to thank all the Celtic fans for the magnificent support they have given me during my time at the club.
“Celtic is a brilliant football club; it will always be in my heart and I will always be a Celtic supporter myself.
“I know Celtic did not want me to leave and wanted to extend my contract. The club did everything to keep me and I appreciate that but I felt the time was right for a new challenge in the English Premier League.
“I thank everyone at the club, the manager and all the staff and I wish Celtic and the fans the very best for the future.”
A spokesperson for Celtic said: “Celtic did absolutely everything we could to keep Virgil at the club, including an offer of a new extended contract on a number of occasions.
“However, it became very clear that he had made his mind up on seeking a new challenge in the English Premier League.
“Virgil has served Celtic very well for the past two seasons, we thank him for his contribution to the club and we wish him all the best for the future at Southampton.”
The Dutchman becomes Koeman’s eighth summer signing following the arrivals of Juani, Cedric Soares, Cuco Martina, Jordy Clasie, Oriol Romeu and Harry Lewis and the loan moves for Maarten Stekelenburg and Caulker.