The Chilean Army commits a massacre of at least 2,000 striking saltpeter miners in Iquique, Chile.

The Chilean Army is the land arm of the Chilean Armed Forces. This 80,000-person army is organized into six divisions, an army aviation brigade and a special operations brigade.

The Santa María School massacre was a massacre of striking workers, mostly saltpeter works (nitrate) miners, along with their wives and children, committed by the Chilean Army in Iquique, Chile, on December 21, 1907. The number of victims is undetermined but is estimated to be over 2,000. The massacre occurred during the peak of the nitrate mining era, which coincided with the Parliamentary Period in Chilean political history (1891–1925). With the massacre and an ensuing reign of terror, not only was the strike broken, but the workers' movement was thrown into limbo for over a decade. For decades afterwards, there was official suppression of knowledge of the incident, but in 2007 the government conducted a highly publicized commemoration of its centenary, including an official national day of mourning and the reinterment of the victims' remains.

Sodium nitrate is the chemical compound with the formula NaNO₃. This alkali metal nitrate salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ordinary saltpeter, potassium nitrate. The mineral form is also known as nitratine, nitratite or soda niter.

Iquique is a port city and commune in northern Chile, capital of both the Iquique Province and Tarapacá Region. It lies on the Pacific coast, west of the Pampa del Tamarugal, which is part of the Atacama Desert. It has a population of 191,468 according to the 2017 census. It is also the main commune of Greater Iquique. The city developed during the heyday of the saltpetre mining in the Atacama Desert in the 19th century. Once a Peruvian city with a large Chilean population, it was conquered by Chile in the War of the Pacific (1879–1883). Today it is one of only two free ports of Chile, the other one being Punta Arenas, in the country's far south.