A magnitude 8.3 earthquake strikes the Valparaíso Region of Chile, killing 177 and leaving nearly a million people homeless.

A megathrust earthquake measuring 8.0 M_w  struck just offshore the Greater Valparaíso area of Central Chile on 3 March 1985. The event followed a ten-day period of moderate and non-destructive foreshocks and left at least 177 people dead and about 2,500 injured. According to several reports, a small sector of damage in Llolleo corresponded to a maximum Mercalli intensity of IX (Violent), though the vast majority of damage was considered to align with intensity VIII (Severe) effects or less. The damage was significant and widespread, and was similar to numerous previous events that had severely impacted the Valparaíso and Santiago metropolitan areas. Great earthquakes related to the subduction zone have occurred directly under populated areas or very close offshore since records began beginning with the arrival of Europeans in the sixteenth-century.

The Valparaíso Region is one of Chile's 16 first order administrative divisions. With the country's second-highest population of 1,790,219 as of 2017, and fourth-smallest area of 16,396.1 km² (6,331 sq mi), the region is Chile's second most densely populated after the Santiago Metropolitan Region to the southeast. The region also includes Chile's remote islands of the Pacific Ocean, including Rapa Nui and the Juan Fernandez Islands.

Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes Mountains and the Pacific Ocean. Chile had a population of 17.5 million as of the latest census in 2017 and has a territorial area of 756,102 square kilometers (291,933 sq mi), sharing borders with Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage to the south. The country also controls several Pacific islands, including Juan Fernández, Isla Salas y Gómez, Desventuradas, and Easter Island, and claims about 1,250,000 square kilometers (480,000 sq mi) of Antarctica as the Chilean Antarctic Territory. The capital and largest city of Chile is Santiago, and the national language is Spanish.