Nicola Sacco (pronounced [niˈkɔːla ˈsakko]; April 22, 1891 – August 23, 1927) and Bartolomeo Vanzetti (pronounced [bartoloˈmɛːo vanˈtsetti, -ˈdzet-]; June 11, 1888 – August 23, 1927) were Italian immigrant anarchists who were controversially accused of murdering Alessandro Berardelli and Frederick Parmenter, a guard and paymaster, during the April 15, 1920, armed robbery of the Slater and Morrill Shoe Company in Braintree, Massachusetts, United States. Seven years later, they were executed in the electric chair at Charlestown State Prison.

After a few hours' deliberation on July 14, 1921, the jury convicted Sacco and Vanzetti of first-degree murder and they were sentenced to death by the trial judge. Anti-Italianism, anti-immigrant, and anti-anarchist bias were suspected as having heavily influenced the verdict. A series of appeals followed, funded largely by the private Sacco and Vanzetti Defense Committee. The appeals were based on recanted testimony, conflicting ballistics evidence, a prejudicial pretrial statement by the jury foreman, and a confession by an alleged participant in the robbery. All appeals were denied by trial judge Webster Thayer and also later denied by the Massachusetts Supreme Judicial Court. By 1926, the case had drawn worldwide attention. As details of the trial and the men's suspected innocence became known, Sacco and Vanzetti became the center of one of the largest causes célèbres in modern history. In 1927, protests on their behalf were held in every major city in North America and Europe, as well as in Tokyo, Sydney, Melbourne, São Paulo, Rio de Janeiro, Buenos Aires, Dubai, Montevideo, Johannesburg, and Auckland.