Sergio Larraín Echeñique (1931 – 7 February 2012) was a Chilean photographer. He worked for Magnum Photos during the 1960s. He is considered the most important Chilean photographer in history.
Photographs he took in Paris by Notre Dame Cathedral, which revealed scenes of a couple only upon processing, became the basis for Julio Cortázar's story, "Las Babas del Diablo", "The Devil's Drool", which in turn inspired Michelangelo Antonioni's 1966 film Blowup.
Born into a professional family in Santiago (his father was an architect), he began by studying music. At the age of 18, he went to the US and studied forestry at the University of California, Berkeley, before transferring to Ann Arbor, Michigan, in 1954. He also travelled through Europe and the Middle East, taking a camera. When he returned home, he began freelancing for the Brazilian magazine O Cruzeiro with a heart-searing series on street children living on the banks of the Rio Mapuche. The Museum of Modern Art in New York acquired two images for its collection in 1956.
In 1958 Larrain obtained a grant from the British Council to undertake an eight-month reportage project on British cities. The book that resulted focused on London, with the swinging 60s just around the corner, capturing the ebb and flow of crowds on the streets and transport system. The work so impressed Henri Cartier-Bresson that he invited Larrain to join the Magnum agency that he had co-founded in 1948, with "Chim" Seymour, George Rodger and Robert Capa.