[4][5] Born in Zaandam, Koeman began his career at Groningen before transferring to the Netherlands' most successful club Ajax in 1983, where they won the national Eredivisie title in 1984–85.

At international level, Koeman was one of the stars of the Netherlands national team, alongside Marco van Basten, Ruud Gullit, Frank Rijkaard and Dennis Bergkamp.

[6] Abroad, he had spells in Portugal with Benfica and Spain with Valencia, coaching Los Ché to victory in the 2007–08 Copa del Rey, and managed Premier League clubs Southampton and Everton in the 2010s.

In August 2020, he was appointed manager of Barcelona, with whom he won the 2020–21 Copa del Rey, but was sacked in October 2021, following a poor start to the new season.

Koeman started his professional career at Groningen, making his debut at the age of 17 years and 183 days in a 2–0 win over NEC in the Eredivisie.

[7] Thirty-three goals from ninety appearances in his three seasons at the club saw the young defender called up by the Netherlands national team and earn a transfer to Eredivisie champions Ajax.

The following season saw Johan Cruyff take over as Ajax head coach and, despite scoring 120 goals in 34 Eredivisie matches and winning the KNVB Cup, de Godenzonen could only finish second in the league behind rivals PSV.

Koeman enjoyed further success with Hiddink and PSV in the following seasons, as the team also won the 1987–88 and 1988–89 Eredivisie titles and the club's first, and to date only, European Cup against Benfica in Stuttgart on 25 May 1988.

[9] Along with players such as Hristo Stoichkov, Romário, Pep Guardiola and Michael Laudrup, Koeman helped the club win La Liga four consecutive seasons years (1991 to 1994).

[12] Koeman was joint-top scorer with eight goals in the 1993–94 UEFA Champions League, in which Barcelona were beaten 0–4 in the final by A.C. Milan at the Olympic Stadium in Athens.

Having retired as a player after his stint with Feyenoord, Koeman became a member of the Netherlands international coaching staff of Guus Hiddink during the 1998 World Cup along with Johan Neeskens and Frank Rijkaard.

This situation, coupled with Ajax being knocked out of the UEFA Cup by Auxerre, 3–2 on aggregate, led Koeman to resign the following day on 25 February 2005.

[19] During Koeman's spell at Ajax, a young Zlatan Ibrahimovic started his rise to international fame, and Wesley Sneijder and Rafael van der Vaart made their debut.

PSV, however, suffered in the second half of the season, also because of injuries of players Jefferson Farfán, Alex and Ibrahim Afellay, obtaining only 19 out 39 possible points.

[31] On 21 July 2011, Koeman was appointed manager of Feyenoord, signing a one-year contract with the Dutch club as replacement for outgoing trainer Mario Been.

[32] Through this appointment, Koeman notably became the first individual ever to serve as both player and head coach at all teams of the so-called "traditional big three" of Dutch football – Ajax, PSV and Feyenoord.

[45] An estimated £150 million was spent on new players, but Koeman admitted that he had not bought a centre forward to replace Romelu Lukaku, the previous season's squad top scorer who had been sold to Manchester United.

[46] Koeman was sacked by the club on 23 October 2017, after his side fell into the relegation zone, following a 2–5 home defeat against Arsenal the previous day.

[49] On 6 February 2018, Koeman was appointed manager of the Netherlands national team on a four-and-a-half-year contract up to and including the 2022 FIFA World Cup.

[53] He took over after Quique Setién had been dismissed from the post[54] following a disastrous 8–2 defeat to Bayern Munich in the quarter final of the 2019–20 UEFA Champions League.

[58] In the following weeks, several disappointing occurred and with yet another loss against Atletico Madrid, Barcelona ended up with their worst league start since 1992, having won only 11 points in the first 8 La Liga matches.

[61] On 11 March, Barcelona were knocked out of the Champions League in the round of 16 against PSG after failing to turn around a 1–4 loss at home, losing 2–5 on aggregate.

On 17 April, Koeman led Barça to a 4–0 win over Athletic Bilbao in the 2021 Copa del Rey Final, gaining revenge for the Supercopa defeat at the same venue three months earlier.

[63] On 29 April, Barcelona were presented with a golden opportunity to go top of La Liga but failed to capitalize after losing out to Granada away 2–1 despite taking the lead.

[67] On 24 October, following Barça's 2–1 defeat against Real Madrid at home, Koeman became the first manager since Patrick O’Connell in 1936 to lose three consecutive Clásicos.

[68] On 28 October, the club announced that Koeman had been relieved of his duties as manager following the team's 1–0 away defeat against Rayo Vallecano, with FC Barcelona sitting at a dissatisfying 9th place on the table.

[84] Regarding his unique run-up and approach to taking free kicks and penalties, Rob Smyth of The Guardian commented in 2009: "We tend to associate Koeman with that particular type of free-kick, where he would lace the ball in a manner that was paradoxically sledgehammer rather than silk, yet if anything he was more adept at the seductive, shorter-range curler.

As with his penalties, when he would charge towards the ball like a man with murder in mind only to tap it gently into the net, part of the skill was in the deception.

"[87] Koeman most commonly organises his teams to have a defensive approach led by their method of attack, whether that be a 4–3–3, a 4-2-3-1 or an alternative, and to defend with minimal space between the lines.

[94] When Erwin was appointed as the head coach of Oman in 2019, they became the first set of brothers to take charge of two different national teams at the same time[95] Koeman is an ambassador for the anti-smoking campaign Kick it with Help.