The Dutchman arrives with big shoes to fill after Pochettino's move to Tottenham, and he is already facing up to the possibility that the likes of Luke Shaw, Dejan Lovren and Adam Lallana could leave the South Coast this summer. Whether they stay or not, Southampton are expected to be busy in the transfer market, and whilst some names are already emerging as to who Koeman is looking to sign, here are three English-based stars who impressed under Koeman during his time with Feyenoord that he could look to reunite with.
Ryo Miyaichi, Arsenal
Japanese youngster Miyaichi has seen his short career so far plagued by injuries, but it's hard to question that the best spell of his career was at Feyenoord under Koeman. The 21-year-old hit three goals in 12 games in the Eredivisie, and when it seemed that his chances of breaking into the first team at Arsenal were dwindling, Koeman admitted his interest in bringing back to Rotterdam.
"It’s right we are also working on Ryo Miyaichi, but at the moment it’s not clear what the situation is," he said last summer. "After that, we can make a step. It’s not that far yet."
A large part of Feyenoord's success last season under Koeman was the pace of Jean-Paul Boetius, and Miyaichi can offer that too. Given the competition for places, at the Emirates Stadium, it's hard to see Arsenal putting up too much of a fight to keep him if Southampton and Koeman come calling.
John Guidetti, Manchester City
Another player at a big Premier League side who has struggled with injuries is Manchester City's Guidetti. And, just like Miyaichi, the most successful period of his career was during a loan spell with Koeman's Feyenoord. Under Koeman's guidance, Guidetti hit a stunning 20 goals in 23 games, prompting the new Saints boss to say the Swedish international could emulate Zlatan Ibrahimovic.
"I think that John can be as good as Zlatan Ibrahimovic," Koeman said in 2012 when Guidetti was with Feyenoord. "I've coached them both. Zlatan struggled a lot more than John to find his way in Netherlands. John is on the same level as players such as Wesley Sneijder and Rafael van der Vaart at that age."
That's huge praise for the 22-year-old, who has barely featured since that amazing season, playing just six games on loan with Stoke last season. With Rickie Lambert gone, Southampton need more firepower - and Koeman is just the man to get Guidetti's career back on track.
Leroy Fer, Norwich City
To go from playing in the Premier League and the World Cup to featuring in the Championship, it's unlikely to be something that appeals to Dutch international Fer. The Norwich City midfielder is in Louis van Gaal's squad in Brazil, but once the Netherlands are knocked out - whenever that may be - Fer will face up to the reality of Championship football after the Canaries were relegated last season.
The 24-year-old featured for a short time at Feyenoord under Koeman before being sold to Twente, but Koeman made it known that he didn't want to sell Fer at all - much less to a divisional rival. Should either Morgan Schneiderlin or Victor Wanyama leave Southampton this summer, Fer could be on Koeman's radar - particularly as Norwich's relegation could hand them a bargain.