The Tiananmen Square protests or the Tiananmen Square Incident, commonly known as the June Fourth Incident (Chinese: 六四事件; pinyin: liùsì shìjiàn, literally the six-four incident) in mainland China, were student-led demonstrations held in Tiananmen Square in Beijing during 1989. The popular national movement inspired by the Beijing protests is sometimes called the '89 Democracy Movement (Chinese: 八九民運; pinyin: bājiǔ mínyùn). The protests started on April 15 and were forcibly suppressed on June 4 when the government declared martial law and sent the military to occupy central parts of Beijing. In what became known as the Tiananmen Square Massacre (Chinese: 天安門大屠殺; pinyin: tiān'ānmén dà túshā), troops with assault rifles and tanks fired at the demonstrators and those trying to block the military's advance into Tiananmen Square. Estimates of the death toll vary from several hundred to several thousand, with thousands more wounded.

Set off by the death of pro-reform Communist general secretary Hu Yaobang in April 1989, amid the backdrop of rapid economic development and social changes in post-Mao China, the protests reflected anxieties about the country's future in the popular consciousness and among the political elite. The reforms of the 1980s had led to a nascent market economy which benefited some people but seriously disaffected others, and the one-party political system also faced a challenge of legitimacy. Common grievances at the time included inflation, corruption, limited preparedness of graduates for the new economy, and restrictions on political participation. The students called for greater accountability, constitutional due process, democracy, freedom of the press, and freedom of speech, although they were highly disorganized and their goals varied. At the height of the protests, about 1 million people assembled in the Square.

As the protests developed, the authorities responded with both conciliatory and hardline tactics, exposing deep divisions within the party leadership. By May, a student-led hunger strike galvanized support for the demonstrators around the country, and the protests spread to some 400 cities. Ultimately, Deng Xiaoping and other Communist Party elders believed the protests to be a political threat and resolved to use force. The State Council declared martial law on May 20 and mobilized as many as 300,000 troops to Beijing. The troops advanced into central parts of Beijing on the city's major thoroughfares in the early morning hours of June 4, killing both demonstrators and bystanders in the process.

The international community, human rights organizations, and political analysts condemned the Chinese government for the massacre. Western countries imposed arms embargoes on China. The Chinese government made widespread arrests of protesters and their supporters, suppressed other protests around China, expelled foreign journalists, strictly controlled coverage of the events in the domestic press, strengthened the police and internal security forces, and demoted or purged officials it deemed sympathetic to the protests. More broadly, the suppression ended the political reforms since 1986 and halted the policies of liberalization in the 1980s, which were only resumed partly after Deng Xiaoping's Southern Tour in 1992. It notably failed to spark major political reforms as opposed to Eastern Bloc protests during the Revolutions of 1989. Considered a watershed event, the protests set the limits on political expression in China up to the present day. Its memory is widely associated with questioning the legitimacy of Communist Party rule and remains one of the most sensitive and most widely censored topics in China.