Ronald Koeman is a Dutch retired footballer who has been manager of the Netherlands national team since 2018. He is the younger brother of his former international teammate Erwin Koeman and the son of former Dutch international Martin Koeman. Koeman was capable of playing both as a defender and as a midfielder; he frequently played as a sweeper, although he was equally known for his goalscoring, long–range shooting, and accuracy from free kicks and penalties.

Born in Zaandam, Koeman began his career at FC Groningen before transferring to the Netherlands' most successful club Ajax, where he won the national Eredivise title in 1984–85. He then joined Ajax's rivals PSV, winning three consecutive Eredivisie titles (1986–87, 1987–88 and 1988–89) and the European Cup in 1988. Ronald Koeman is one of five European players to ever win a Treble with their club and a cup with their national team in the same year. The other four players are his teammates Hans van Breukelen, Berry van Aerle, Gerald Vanenburg and Wim Kieft. In 1989, Koeman moved to Barcelona and became part of Johan Cruyff's "Dream Team", helping the club win La Liga four years in a row between 1991 and 1994, and the European Cup, where he scored the winning goal of the final against Sampdoria in 1992.

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. During his career with the Netherlands, Koeman won UEFA Euro 1988 and played at the UEFA Euro 1992, 1990 and 1994 FIFA World Cups, captaining the team at the latter.

As a head coach, Koeman has won three Eredivisie titles: twice with Ajax (2001–02 and 2003–04) and once with PSV (2006–07). He is the only individual to have both played for and managed the "Big Three" of Dutch football: Ajax, PSV and Feyenoord. Abroad, he had spells in Portugal with Benfica and Spain with Valencia, coaching Los Che to victory in the 2007–08 Copa del Rey, and managed Premier League clubs Southampton and Everton in the 2010s.