The Ustaše Militia (Ustaška vojnica) was the military branch of the Ustaše, established by the fascist regime of Ante Pavelić in the Independent State of Croatia (NDH), an Axis puppet state established from a large part of occupied Yugoslavia during World War II.
The militia went through a series of re-organisations during its existence, expanding to include all armed elements of the NDH government outside of the Croatian Home Guard, Navy, and Air Force. It amalgamated with the Home Guard in December 1944 and January 1945 to form the Croatian Armed Forces (Hrvatske oružane snage, HOS), although the amalgamation did not result in a homogeneous organisation; former Ustaše militia officers dominated HOS's operations and held most command positions.
The Ustaše militia committed some of the worst atrocities of World War II, including playing a key role in the establishment and operation of about 20 concentration camps in the NDH. Its units included the Black Legion (Crna Legija), commanded by Jure Francetić and Rafael Boban, and the Ustaše Defence Brigades, commanded by Vjekoslav Luburić.
The Ustaše militia was created on 11 April 1941 when Marshal Slavko Kvaternik appointed a separate staff to control the various volunteer armed groups that had risen spontaneously throughout the NDH as the Yugoslav Army collapsed in the face of the Axis invasion. On 10 May 1941, Ante Pavelić issued a special order which detailed its formal organisation. However, some of the groups that formed early were irregular or "wild" Ustaše units that were not included in the formal organisation, which initially numbered 4,500. The number of irregular Ustaše across the NDH was reportedly as high as 25,000–30,000. Both formal and irregular units were soon involved in atrocities against Serbs, Jews, Gypsies, and all alleged and actual opponents of the Ustaše regime.
The militia consisted mostly of volunteers, and only 25% of the officer corps were professionally trained. Members were indoctrinated in Ustaše ideology and committed to defending Pavelić and the Ustaše regime.