The Arditi del Popolo was an Italian militant anti-fascist group founded at the end of June 1921 to resist the rise of Benito Mussolini's National Fascist Party and the violence of the Blackshirts (squadristi) paramilitaries. It grouped revolutionary trade-unionists, socialists, communists, anarchists, republicans, anti-capitalists, as well as some former military officers, and was co-founded by Giuseppe Mingrino, Argo Secondari and Gino Lucetti – who tried to assassinate Mussolini on 11 September 1926 – the deputy Guido Picelli and others. The Arditi del Popolo were an offshoot of the Arditi elite troops, who had previously occupied Fiume in 1919 behind the poet Gabriele d'Annunzio, who proclaimed the Italian Regency of Carnaro. Those who split to form the Arditi del Popolo were close to the anarchist Argo Secondari and were supported by Mario Carli. The formazioni di difesa proletaria later merged with them. The Arditi del Popolo gathered approximately 20,000 members in summer 1921.

Anti-fascism is a political movement in opposition to fascist ideologies, groups and individuals. Beginning in European countries in the 1920s, it was at its most significant shortly before and during World War II, where the Axis powers were opposed by many countries forming the Allies of World War II and dozens of resistance movements worldwide. Anti-fascism has been an element of movements across the political spectrum and holding many different political positions such as anarchism, communism, pacifism, republicanism, social democracy, socialism and syndicalism as well as centrist, conservative, liberal and nationalist viewpoints.