Deployed primarily as a centre back but occasionally as a right back, a position where he started his career, Koscielny plays for Arsenal and the French national football team. Described as an aggressive, strong, quick and ball-playing defender, he was voted as Wenger's most effective signing of 2010-11 following an impressive debut campaign. Koscielny was called up to the French national team on 4 February 2011 and represented the country at UEFA Euro 2012 and the 2014 FIFA World Cup.
His career began in 2004 with Guingamp before moving to Tours FC, Lorient and Arsenal on 7 July 2010.
He was born in Tulle, France.