Koeman, 51, recently led Feyenoord to second place in the Eredivisie, but left the club at the end of the season in search of a big move. That has now come after Southampton announced that the former Dutch international has been chosen as the man to replace Mauricio Pochettino, who left the South Coast for a move to Tottenham.
After a superb career as a player, Koeman has had an indifferent time as a manager, particularly struggling with Valencia before rebuilding his reputation with Feyenoord back in his native Holland. He has a tough task on his hands at St. Mary's Stadium though, with the likes of Dejan Lovren, Luke Shaw and Adam Lallana all linked with moves away from the club this summer.
It seems that he won't be able to keep hold of Croatian international Lovren, and he has already reportedly made plans for his departure - by eyeing up a swoop for Celtic defender van Dijk.
The 22-year-old has starred for Celtic this season after signing for just £2.6m from Groningen, and after a superb season, his value has now shot up to around £8m - and Koeman is willing to pay it in order to bring him down to England.
The Saints aren't the only team interested in a move for the young Dutchman, as it was repeatedly speculated throughout the season that Manchester United had been watching van Dijk with intent, knowing that experienced duo Nemanja Vidic and Rio Ferdinand would be leaving the club.
Despite their exit, it seems unlikely that United would rekindle their interest in van Dijk, particularly because new manager Louis van Gaal has been coaching the Dutch national team, and despite their need for defensive help, he has repeatedly shunned van Dijk from his team - which could leave Southampton in the clear to land the centre half.