The Shanghai massacre of 12 April 1927, the April 12 Purge or the April 12 Incident as it is commonly known in China, was the violent suppression of Chinese Communist Party (CCP) organizations and leftist elements in Shanghai by forces supporting General Chiang Kai-shek and conservative factions in the Kuomintang (Chinese Nationalist Party or KMT). Between 12 and 14 April, hundreds of communists in Shanghai were arrested and killed on the orders of Chiang. The ensuing White Terror devastated the Communists, and only 10,000 out of 60,000 party members survived.

Following the incident, conservative KMT elements carried out a full-scale purge of Communists in all areas under their control, and violent suppression occurred in Guangzhou and Changsha. The purge led to an open split between left-wing and right-wing factions in the KMT, with Chiang Kai-shek establishing himself as the leader of the right-wing faction based in Nanjing, in opposition to the original left-wing KMT government based in Wuhan, which was led by Wang Jingwei.

By 15 July 1927, the Wuhan regime had expelled the Communists in its ranks, effectively ending the First United Front, a working alliance of both the KMT and CCP under the tutelage of Comintern agents. For the rest of 1927, the CCP would fight to regain power, beginning the Autumn Harvest Uprising. With the failure and the crushing of the Guangzhou Uprising at Guangzhou however, the power of the Communists was largely diminished, unable to launch another major urban offensive.