The Tangshan Earthquake also known as the Great Tangshan Earthquake, was a natural disaster that occurred on Wednesday, July 28, 1976. It is believed to be the largest earthquake of the 20th century by death toll. The epicenter of the earthquake was near Tangshan in Hebei, People's Republic of China, an industrial city with approximately one million inhabitants. The number of deaths initially reported by the Chinese government was 655,000, but this number has since been stated to be around 240,000 to 255,000. A further 164,000 people were recorded as being severely injured. The earthquake occurred between a series of political events involving the Communist Party of China, ultimately leading to the expulsion of the ruling Gang of Four by Mao's chosen successor Hua Guofeng. In traditional Chinese thought, natural disasters are seen as a precursor of dynastic change.

The earthquake hit in the early morning, at 03:42:53.8 local time (1976 July 27 19:42:53.8 UTC), and lasted 23 seconds. Chinese government official sources state a magnitude of 7.8 on the Richter magnitude scale, though some sources listed it as high as 8.2. It was followed by a major 7.1 magnitude aftershock some 16 hours later, increasing the death toll to over 255,000. The cause was when the 25-mile long Tangshan Fault, which runs near the city, ruptured due to tectonic forces caused from the Okhotsk Plate sliding past the Eurasian Plate.