The Ninth Army (French: IXe Armée) was a Field army of the French Army during World War I and World War II.
The Ninth Army, first named "détachement d'armée Foch", was formed for the first time on 29 August 1914, to fill the gap between the Fourth and Fifth Army. It played an important role in the first Battle of the Marne. The Ninth Army was disbanded on 5 October 1914, when Foch became commander of Army Group North.
The Ninth Army was recreated on 6 July 1918 under command of Antoine de Mitry to fight in the Second Battle of the Marne.
In 1940, it was initially the only part of the French army that faced the Germans directly as they came unexpectedly through the Ardennes during the early stages of the Fall of France.