Southampton have completed the signing of Dutch defender Virgil van Dijk on a five-year deal from Scottish champions Celtic.
The 24-year-old had been heavily linked with a move to the Premier League club for much of the window and eventually put pen to paper on Tuesday.
Formerly of Eredivisie side Groningen, Van Dijk has impressed at Parkhead but always looked likely to leave following Celtic's UEFA Champions League exit last week.
Ronny Deila's men were beaten 4-3 on aggregate by Malmo in the competition's play-off round.
Van Dijk told Southampton's official website: "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. 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 quickly, 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."
The Dutchman could make his debut for Ronald Koeman's side at West Brom after the international break.
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