The Maxi Trial (Italian: Maxiprocesso) was a criminal trial against the Sicilian Mafia that took place in Palermo, Sicily. The trial lasted from 10 February 1986 (the first day of the Corte d'Assise) to 30 January 1992 (the final day of the Supreme Court of Cassation), and was held in a bunker-style courthouse specially constructed for this purpose inside the walls of the Ucciardone prison.

Sicilian prosecutors indicted 475 mafiosi for a multitude of crimes relating to Mafia activities, based primarily on testimonies given as evidence from former Mafia bosses turned informants, known as pentiti, in particular Tommaso Buscetta and Salvatore Contorno. Most were convicted, 338 people, sentenced to a total of 2,665 years, not including life sentences handed to 19 bosses; the convictions were upheld on 30 January 1992 by the Supreme Court of Italy, after the final stage of appeal. The importance of the trial was that the existence of Cosa Nostra was finally judicially confirmed.

It is considered to be the most significant trial ever against the Sicilian Mafia, as well as the largest trial in world history. Throughout and after the trial, several judges and magistrates were killed by the Mafia, including the two who led it—Giovanni Falcone and Paolo Borsellino.