Association Culturelle et Sportive du Ksar (Arabic: الجمعية الثقافية و الرياضية للكصر) known as ACS Ksar is a Mauritanian football club based in Nouakchott the capital of the Mauritania. The club plays in the Ligue 1 Mauritania.
The club was founded in 1978 in the Ksar neighborhood of Nouakchott. It was known in the 1990s under the name of ASC Sonader Ksar (Association Sportive et Culturelle Sonader Ksar) when it was sponsored by SONADER (Sociètè Nationale pour le Développement Rural).
Ksar won their first title in 1983, their second in 1983. The club won two consecutive titles in 1993, Ksar first appeared at the continental level in 1992. Ksar won their recent championship title in 2004 and a year later entered into their recent continental competition and their first and only as the CAF Champions League.
Ksar won their first cup title in 1979 and brought Ksar to their only continental appearance. Ksar (then also known as SONADER) won two consecutive cup titles in 1994, the club did not enter the continental cup competition. Their recent cup title was won in 2014. Ksar won their only Super Cup title in 2014 as Ksar entered as cup winner.
Ksar appeared once in the Arab Champions' League (now the UAFA Club Cup) in the 2005–06 season.
At the continentals, all clubs they challenged were from the westernmost part and the northernmost part of the continent, two are sub-Saharan clubs.