The Organisation Spéciale (OS, Special Organisation) was a secret paramilitary organization in the French colony of Algeria, created by the Parti du Peuple Algerien (PPA, Algerian People's Party) during a convention of the Mouvement pour le Triomphe des Libertés Démocratiques (MTLD, Movement for the Triumph of Democratic Liberties) in 1947. It was a response to the Sétif Massacre of May 1945 in which thousands were killed.
The OS had a couple of thousand members and led to the development of the FLN which led the Algerian War of Independence (1954-62) and then became Algeria's ruling party until 1992.
The OS was ostensibly broken up by the French authorities in 1951, although a few pockets of resistance remained ensconced in the Atlas mountains.
