Indonesian mass killings of 1965–66

From October 1965 to March 1966, a series of large-scale killings and civil unrest primarily targeting members and supposed sympathizers of the Communist Party of Indonesia (PKI) took place in Indonesia. Other affected groups included alleged communist sympathisers, Gerwani women, trade unionists, ethnic Javanese Abangan, ethnic Chinese, atheists and other non-Muslims, and leftists in general. According to the most widely published estimates, at least 500,000 to 1 million people were killed. Some of the higher estimates reach figures as much as 2 to 3 million.

The killings, sometimes described as a politicide and occasionally as a genocide, although there is no scholarly consensus on the latter, were instigated by the Indonesian Army under Suharto. Research and declassified documents demonstrate the Indonesian authorities received support from foreign countries such as the United States and the United Kingdom.

The killings began as an anti-communist purge following an attempted coup d'état by the 30 September Movement, which they self-proclaimed over media and communication outlets. It was a pivotal event in the transition to the "New Order" and the elimination of PKI as a political force, with impacts on the global Cold War. The Army, after banning all independent news sources from publishing for a week, almost immediately pinned the abortive coup attempt to the PKI.

Concurrently, the intelligence agencies of the United States, United Kingdom, and Australia engaged in black propaganda campaigns against Indonesian communists. During the Cold War, the U.S. government and its Western allies had the goal of halting the spread of communism in addition to bringing countries into the sphere of Western Bloc influence. Separately, Britain had reasons for seeking Sukarno's removal, as his non-communist government was involved in an undeclared war with neighboring Malaysia, a Commonwealth federation of former British colonies.

Communists were purged from political, social, and military life in Indonesia, and the PKI itself was disbanded and banned. Mass killings began in October 1965, in the weeks following the coup attempt, and reached their peak over the remainder of the year before subsiding in the early months of 1966. They started in the capital, Jakarta, and spread to Central and East Java, and later Bali. Thousands of local vigilantes and army units killed actual and alleged PKI members, as well as members of other marginalized groups. Killings occurred across the country, with the most intense in the PKI strongholds of Central Java, East Java, Bali, and northern Sumatra. The upheavals led to the fall of Sukarno, who had been granted the title "President for life", and ushering in Suharto's three decades of pro-West authoritarian militaristic presidency.

The killings are skipped over in most Indonesian history textbooks and have received little attention by Indonesians due to their suppression under the Suharto regime, as well as lack of international attention. The search for satisfactory explanations for the scale and frenzy of the violence has challenged scholars from all ideological perspectives. The possibility of returning to similar upheavals is cited as a factor in the "New Order" administration's political conservatism and tight control of the political system. Vigilance and stigma against a perceived communist threat remained a hallmark of Suharto's doctrine, and it is still in force even today.

Despite a consensus at the highest levels of the U.S. and British governments that it would be necessary "to liquidate Sukarno", as related in a Central Intelligence Agency (CIA) memorandum from 1962, and the existence of extensive contacts between anti-communist army officers and the U.S. military establishment – including the training of over 1,200 officers, "including senior military figures", and providing weapons and economic assistance – the CIA denied active involvement in the killings. Declassified U.S. documents in 2017 revealed that the U.S. government had detailed knowledge of the mass killings from the beginning and was supportive of the actions of the Indonesian Army. U.S. complicity in the killings, which included providing extensive lists of PKI officials to Indonesian death squads, has been established by historians and journalists.

A top-secret CIA report from 1968 stated that the massacres "rank as one of the worst mass murders of the 20th century, along with the Soviet purges of the 1930s, the Nazi mass murders during the Second World War, and the Maoist bloodbath of the early 1950s."