The Italian Civil War was a civil war in the Kingdom of Italy fought during World War II from 8 September 1943 (the date of the Armistice of Cassibile) to 2 May 1945 (date of the Surrender of Caserta), by the Italian Fascists of the Italian Social Republic, a collaborationist puppet state created under the direction of Nazi Germany during its occupation of Italy, against the Italian partisans (mostly politically organized in the National Liberation Committee), materially supported by the Allies, in the context of the Italian campaign. The Italian partisans and the Italian Co-Belligerent Army of the Kingdom of Italy simultaneously fought against the occupying Nazi German armed forces. Armed clashes between the National Republican Army of the Italian Social Republic and the Italian Co-Belligerent Army of the Kingdom of Italy were rare, while there was some internal conflict within the partisan movement. In this context, Germans, sometimes helped by Italian Fascists, committed several atrocities against Italian civilians and troops.

The event that later gave rise to the Italian Civil War was the deposition and arrest of Benito Mussolini on 25 July 1943 by King Victor Emmanuel III, after which Italy signed the Armistice of Cassibile on 8 September 1943, ending its war with the Allies. However, German forces began occupying Italy immediately prior to the armistice, through Operation Achse, and then invaded and occupied Italy on a larger scale after the armistice, taking control of northern and central Italy and creating the Italian Social Republic (RSI), with Mussolini installed as leader after he was rescued by German paratroopers in the Gran Sasso raid. As a result, the Italian Co-Belligerent Army was created to fight against the Germans, while other Italian troops, loyal to Mussolini, continued to fight alongside the Germans in the National Republican Army. In addition, a large Italian resistance movement started a guerrilla war against the German and Italian fascist forces. The anti-fascist victory led to the execution of Mussolini, the liberation of the country from dictatorship, and the birth of the Italian Republic under the control of the Allied Military Government of Occupied Territories, which was operational until the Treaty of Peace with Italy in 1947.