The Black Liberation Army (BLA) was an underground Marxist-Leninist, black-nationalist militant organization that operated in the United States from 1970 to 1981. Composed of former Black Panthers (BPP) and Republic of New Afrika (RNA) members who served above ground before going underground, the organization's program was one of war against the United States government, and its stated goal was to "take up arms for the liberation and self-determination of black people in the United States." The BLA carried out a series of bombings, killings of police officers and drug dealers, robberies (which participants termed "expropriations"), and prison breaks.

The Black Liberation Army gained strength as Black Panther Party membership declined. By 1970, police and FBI sabotage (see COINTELPRO), infiltration, sectarianism, the lengthy prison sentences, and death of key members (among them Fred Hampton) had significantly undermined the Black Panther Party. This convinced many former party members of the desirability of underground existence, seeing that a new period of violent repression by the U.S federal and local government was at hand. BLA members operated under the belief that only through covert means, including but not limited to retribution, could the movement be continued until such a time when an above-ground existence was possible. The conditions under which the Black Liberation Army formed are not entirely clear. It is commonly believed that the organization was founded by those who left the Black Panther Party after Eldridge Cleaver was expelled from the party's Central Committee. A fallout between Cleaver and other Panther leaders followed from his public criticism of the BPP, among other things accusing Panther social programs of being reformist rather than revolutionary. Others, including black revolutionary Geronimo Pratt (AKA Geronimo ji Jaga), assert that the BLA "as a movement concept pre-dated and was broader than the BPP," suggesting that it was a refuge for ex-Panthers rather than a new organization formed through schism. Assata Shakur, in her autobiography, Assata: An Autobiography, asserts: “the Black Liberation Army was not a centralized, organized group with a common leadership and chain of command. Instead, there were various organizations and collectives working together and simultaneously independent of each other.”

According to a Justice Department report on
BLA activity, the Black Liberation Army was suspected of involvement in over 70 incidents of violence between 1970 and 1976. The Fraternal Order of Police blamed the BLA for the murders of 13 police officers.

The BLA was active in the US until at least 1981 when a Brinks truck robbery, conducted with support from former Weather Underground members Kathy Boudin, David Gilbert and Judith Alice Clark, left a guard and two police officers dead. Boudin, Gilbert and Clark along with several BLA and May 19 Communist Organization members, were subsequently arrested.

Following the collapse of the BLA, some members - including Ashanti Alston, Donald Weems (a.k.a. Kuwasi Balagoon) and Ojore Lutalo - became outspoken proponents of anarchism. Weems died in prison of an AIDS-related disease in 1986. Alston remains active in prison support and other activist circles. Lutalo was released from prison in 2009 after serving 28 years on charges related to a shootout with a drug dealer in 1981 (and parole violation stemming from his conviction for a 1975 bank robbery), during which time he was punished with solitary confinement for receiving anarchist literature. While incarcerated, the Anarchist Black Cross Federation gave him support.