Kalidou Koulibaly was born on 20 June, 1991 to Senegalese parents in Saint-Dié-des-Vosges, France. His footballing career began with local club SR Saint-Dié. He is a Senegalese footballer who plays as defender for Serie A club Napoli and the Senegal national football team, usually as a centre-back. A large, quick and physically strong yet elegant player, he is recognized for his aerial prowess, anticipation, passing ability and versatility, as he can play both as a central defender, or as a full-back on either the right or left flank, in both a three or four-man defence; he has even been deployed as a defensive midfielder. His playing style has earned him the nicknames K2 and The Wall from his fans.
Kalidou began his career playing for his hometown club SR Saint-Dié’s youth team, and spent two seasons playing on the club’s senior team in the Championnat de France amateur 2, before joining the youth academy of professional club Metz on 1 July 2009. While at Metz, he helped the club’s under-19 team win the 2009–10 Coupe Gambardella after the team defeated Sochaux 5–4 on penalties in the final. He also played on the club’s amateur team in the Championnat de France amateur appearing in 15 matches as Metz were crowned champions of the league finishing with 107 points.
Koulibaly began his professional club career with French side Metz in 2010, before moving to Belgian club Genk in 2012. He joined Italian side Napoli in 2014, where he soon established himself as one of the best defenders in Italy. As he was born in France to Senegalese parents, he was eligible to represent both nations at international level, and initially played for the France national under-20 football team. He later made his senior debut with Senegal in 2015, and was a member of the Senegal squad that took part at the 2017 Africa Cup of Nations.
In early September 2015, Koulibaly changed federations and joined the Senegal national football team, despite the interest to call him for Les Bleus from Didier Deschamps. He made his debut on 5 September 2015 in an AFCON qualifier against Namibia in a 2–0 victory. He was a member of the Senegal squad that took part at the 2017 Africa Cup of Nations.