Three Souths Affair (Indonesian: Peristiwa Tiga Selatan) was a failed alleged-coup attempt by Communist Party of Indonesia in South Sulawesi, South Sumatra, and South Kalimantan. The three regions was chosen because it was deemed by D. N. Aidit as having numerous supporters of communism and out of reach of the Indonesian Army which its stronghold mostly in Java. The armed rebellion was later suppressed and the Communist Party was banned in the three provinces.
Hasan Basry as military governor of South Kalimantan reacted strongly to this, immediately banned any activities related to communism, causing disagreement with Sukarno. The conflict caused more friction between Indonesian Army & Communist Party, which later led to 30 September Movement.