The Dutch defender agreed a five-year contract with the South Coast club, after a summer-long transfer saga that saw the move delayed until the closing hours of the transfer window.
The 24-year-old moved to Celtic in 2013 from Eredivisie side Groningen, and made 114 appearances for the Bhoys in his stay in Scotland. He netted an impressive 15 goals from defence, and although he occasionally struggled in European competitions, Van Dijk have proven that he was far too good for the Scottish Premiership.
His move to Southampton follows their transfer philosophy of signing young and fairly cheap players who can continue to develop under the tutelage of Ronald Koeman, and the head coach could play a vital role in Van Dijk’s development - having been a goalscoring centre-back in his own playing years.
Van Dijk looks to have all the talent needed to be a success in the Premier League, and fans of both Southampton and Celtic took to Twitter to react to the confirmation of his move to England.
Ecstatic van Dijk has signed. We needed a quality CB with Fonte as good as Alderweireld. Well done Les Reed for pulling it off #SaintsFC— Joseph Richardson (@Jj147Joseph) September 1, 2015
Good to have "the Rhythm of Van Dijk" now at the back for #saintsfc good replacement for TA and massive improvement on Maya/Gardos— MLC (@matt_lecornu) September 1, 2015
@BBCMOTD Great Move Him And Fonte Deadly Partnership— ●☆♤♡JHÂŁĖËĹ◇♧☆● (@Jhaleel_RK) September 1, 2015
@BBCMOTD Bloody excellent business. A young centre half, good on the ball and breaking into hus international side.— Matthew Dev (@MatthewJBD) September 1, 2015
Great piece of business by @Celticfc getting that much for Van Dijk - undoubtedly a good player, but was Denayer the better of the two...— Séan Walsh (@walshybhoy) September 1, 2015
What a deal by Celtic. Great business. Van Dijk was a liability from the moment he got a sniff of the premier league.— Paul Friel (@friellyboy) September 1, 2015
11.5 mill for big van dijk is a great bit a business.— Thomas Shaw (@RealThomasShaw) September 1, 2015
Van Dijk deal is great for Celtic. Another example to give to promising players to endure the SPFL and you'll get your payday eventually.— Aidan Kerr (@Aidan_Kerr1) September 1, 2015
£11.5 - 13m for Van Dijk is a great piece of business. I would love us to go and buy a LB to take Izzys place in the team. #Celtic— Adam Baxter (@17SecondsHawks) September 1, 2015