Operación Masacre (English: "Operation Massacre") is a nonfiction novel of investigative journalism, written by noted Argentine journalist and author Rodolfo Walsh.

[1] It was published in 1957, nine years before the publication of Truman Capote's In Cold Blood, a book often credited as the first major nonfiction novel of investigative journalism.

These events followed a 1955 military coup, known as Revolución Libertadora ("the Liberating Revolution"), which deposed Argentine president Juan Perón and eventually brought the right-wing dictatorship to power, led first by Lieutenant General Eduardo Lonardi – who was considered too "lenient" (with Peronism) by the leaders of the coup and quickly deposed – and later by the hard-line General Pedro Eugenio Aramburu.

"[7] The novel explores themes of violence that are not only unexpected, but are also unpunished,[8] although Pedro Eugenio Aramburu would ultimately be executed in 1970 by the Peronist Montoneros for his role in the José León Suárez massacre.

[10] Operación Masacre was adapted into a 1973 drama film written and directed by Jorge Cedrón and starring Norma Aleandro, Carlos Carella, Víctor Laplace, Ana María Picchio and one of the survivors of the José León Suárez massacre, Julio Troxler.