London - Southampton have signed Dutch defender Virgil van Dijk from Scottish champions Celtic, the Premier League club announced on Tuesday.
Van Dijk agreed a five-year contract with Ronald Koeman's side and is reported to have cost Saints £11.5 million.
The 24-year-old will compete with Jose Fonte, Maya Yoshida and Steven Caulker for a place in the centre of Southampton's defence.
"I'm delighted. It was a very easy decision to join this club. This is a very ambitious club, who have been doing very well in the last couple of years," Van Dijk told Southampton's website.
"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'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."
Van Dijk is Koeman's ninth signing since the end of last season following the arrivals of Juanmi, Cedric Soares, Cuco Martina, Jordy Clasie, Oriol Romeu and Harry Lewis and loan moves for Maarten Stekelenburg and Caulker.
He started his professional career with Groningen in 2011 and joined Celtic two years later.
Van Dijk spent just over two years in Glasgow, playing more than 100 times and scoring 15 goals, and helped Celtic win the Scottish league title in 2014 and 2015.
He has represented the Netherlands at under-21 and under-19 levels, but is yet to make his senior international debut.