She wrote about the FBI's targeting of the Black Panther Party as part of its Counter Intelligence Program (COINTELPRO). Also, she was tried and acquitted of suspected involvement in the Soledad brothers' August 1970 abduction and murder of Judge Harold Haley in Marin County, California, even though she had purchased the weapons involved, had written letters to one of the prisoners who had escaped, and became a fugitive of the law after the murders. She was twice a candidate for Vice President on the Communist Party USA ticket during the Reagan era.

Since moving in the early 1990s from party communism to other forms of political commitment, she has identified herself as a democratic socialist. Davis is the founder of "Critical Resistance", an organization working to abolish the prison-industrial complex.

Davis was born in Birmingham, Alabama. Her father, Frank Davis, was a graduate of St. Augustine's College, a traditionally black college in Raleigh, North Carolina, and was briefly a high school history teacher. Her father later owned and operated a service station in the black section of Birmingham. Her mother, Sallye Davis, a graduate of Miles College in Birmingham, was an elementary school teacher.

The family lived in the "Dynamite Hill" neighborhood, which was marked by racial conflict. Davis was occasionally able to spend time on her uncle's farm and with friends in New York City. Her brother, Ben Davis, played defensive back for the Cleveland Browns and Detroit Lions in the late 1960s and early 1970s.

Davis attended Carrie A. Tuggle School, a black elementary school; later she attended Parker Annex, a middle-school branch of Parker High School in Birmingham. By her junior year, she had applied to and was accepted at an American Friends Service Committee program that placed black students from the South in integrated schools in the North. She chose Elisabeth Irwin High School in Greenwich Village in New York City. There she was introduced to socialism and communism and was recruited by a Communist youth group, Advance. She also met children of some of the leaders of the Communist Party USA, including her lifelong friend, Bettina Aptheker.

Davis was awarded a scholarship to Brandeis University in Waltham, Massachusetts, where she was one of three black students in her freshman class. She initially felt alienated by the isolation of the campus (at that time she was interested in Albert Camus and Jean-Paul Sartre), but she soon made friends with foreign students. She encountered the Frankfurt School philosopher Herbert Marcuse at a rally during the Cuban Missile Crisis and then became his student. In a television interview, she said "Herbert Marcuse taught me that it was possible to be an academic, an activist, a scholar, and a revolutionary." She worked part time to earn enough money to travel to France and Switzerland before she went on to attend the eighth World Festival of Youth and Students in Helsinki, Finland. She returned home in 1963 to an FBI interview about her attendance at the Communist-sponsored festival.

During her second year at Brandeis, she decided to major in French and continued her intensive study of Sartre. Davis was accepted by the Hamilton College Junior Year in France Program and, she wrote in her autobiography, she managed to talk Brandeis into extending financial support via her scholarship. Classes were initially at Biarritz and later at the Sorbonne. In Paris, she and other students lived with a French family. It was at Biarritz that she received news of the 1963 Birmingham church bombing, committed by the members of the Ku Klux Klan, an occasion that deeply affected her, because, she wrote, she was personally acquainted with the eight young victims.

Nearing completion of her degree in French, Davis realized her major interest was in philosophy. She became particularly interested in the ideas of Herbert Marcuse and on her return to Brandeis she sat in on his course without asking for credit. Marcuse, she wrote, turned out to be approachable and helpful. Davis began making plans to attend the University of Frankfurt for graduate work in philosophy. In 1965 she graduated magna cum laude, a member of Phi Beta Kappa.

In Germany, with just a stipend of $100 a month, she first lived with a German family. Later, she moved with a group of students into a loft in an old factory. After visiting East Berlin during the annual May Day celebration, she felt that the East German government was dealing better with the residual effects of fascism than were the West Germans. Many of her roommates were active in the radical Socialist German Student Union (SDS), and Davis participated in SDS actions, but events unfolding in the United States — the formation of the Black Panther Party and transformation of SNCC, for example — impelled her to return to the US.

Marcuse, in the meantime, had moved to the University of California, San Diego, and Davis followed him there after her two years in Frankfurt.