The Acteal Massacre was a massacre of 45 people (although some sources claim 60 or more) attending a prayer meeting of Roman Catholic activists for indigenous causes in the small village of Acteal in the Mexican state of Chiapas. It was carried out on December 22, 1997 by paramilitary forces widely assumed to have close ties to figures in the federal military and in the federal and Chiapas state governments, although the extent of knowledge and involvement of government figures is a source of controversy.

The Roman Catholic activists professed support for the goals of the EZLN ("Zapatista") rebels, which is almost certainly the reason for the attack on the prayer meeting (though the activists did distance themselves from the EZLN's methods). The main source of controversy is over who organized and ordered the paramilitary attack. Some government involvement seems almost certain, but opinion differs over whether the attack was centrally organized by the political establishment (possibly including either Chiapas governor Julio César Ruiz or Mexican president Ernesto Zedillo, or both); was organized by the army without the knowledge of the political leadership; was organized by a branch of the army; or was organized by rogue army officers in control of private militias. The EZLN, along with many Chiapas residents (particularly the indigenous population) blamed the ruling Institutional Revolutionary Party (PRI) for the massacre, and even after a change of government in 2000, survivors alleged that the investigation was being stalled, with authorities refusing to question or arrest any suspects in the attacks.