Autodefensas Unidas de Colombia (United Self-Defense Forces) or AUC is an terrorist umbrella organization formed in April 1997 to consolidate most local and regional paramilitary groups in Columbia, each with the mission to protect economic interests and combat insurgents locally. The AUC claims its primary objective is to protect its sponsors from insurgents. The AUC now asserts itself as a regional and national counterinsurgent force. AUC leader Carlos Castaņo in 2000 claimed 70 percent of the AUC's operational costs were financed with drug-related earnings, the rest coming from "donations" from its sponsors.

According to the Colombian National Police in the first ten months of 2000 the AUC conducted 804 assassinations, 203 kidnappings, and 75 massacres with 507 victims. The AUC claims the victims were guerrillas or sympathizers. Combat tactics consist of conventional and guerilla operations against main force insurgent units. AUC clashes with military and police units are increasing, although the group has traditionally avoided government security forces.