The Blagaj massacre was the mass killing of around 400 Serb civilians by the Croatian nationalist Ustaše movement on 9 May 1941, during World War II. The massacre occurred shortly after the German-led Axis invasion of Yugoslavia and the establishment of the Ustaše-led Axis puppet state known as the Independent State of Croatia (NDH). It was the second act of mass murder committed by the Ustaše upon coming to power and was part of a wider campaign of genocide against Serbs in the NDH that would last until the end of the war.