The Voluntary Militia for National Security, commonly called the Blackshirts or squadristi, was originally the paramilitary wing of the National Fascist Party, known as the Squadrismo, and after 1923 an all-volunteer militia of the Kingdom of Italy under Fascist rule, similar to the SA. Its members were distinguished by their black uniforms and their loyalty to Benito Mussolini, the Duce (leader) of Fascism, to whom they swore an oath. The founders of the paramilitary groups were nationalist intellectuals, former army officers and young landowners opposing peasants' and country labourers' unions. Their methods became harsher as Mussolini's power grew, and they used violence and intimidation against Mussolini's opponents. In 1943, following the fall of the Fascist regime, the MVSN was integrated into the Royal Italian Army and disbanded.

A paramilitary is a military that is not part of a country's official or legitimate armed forces. The Oxford English Dictionary traces the use of the term "paramilitary" as far back as 1934.