The Ustaše Militia was the military branch of the Ustaše, established by the fascist and genocidal 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 Ustaše, also known by anglicised versions Ustasha or Ustashe, was a Croatian, fascist and ultranationalist organization active, as one organization, between 1929 and 1945, formally known as the Ustaša – Croatian Revolutionary Movement. Since the inception and before the Second World War, its members engaged in a series of terrorist activities against the Kingdom of Yugoslavia, including collaborating with IMRO to assassinate King Alexander I of Yugoslavia in 1934. After the invasion of Yugoslavia by Axis forces in April 1941, the Ustaše were handed power by the occupying forces and formed the Independent state of Croatia, an Axis puppet state, and immediately went on to perpetrate the Holocaust and genocide against its Jewish, Serb and Roma populations. During the World War II in Yugoslavia, together with German and Italian occupying forces, Ustaše are responsible for killing of hundreds of thousands of Serbs, Jews, Roma, as well as Bosniak Muslim and Croat political dissidents.