The Manson Family (known among its members as the Family) was a commune, gang and cult led by criminal Charles Manson that was active in California in the late 1960s and early 1970s. At its peak the group consisted of approximately 100 followers who lived an unconventional lifestyle, frequently using psychoactive drugs, including amphetamine and hallucinogens such as LSD. Most were young women from middle-class backgrounds, many of whom were attracted by hippie counterculture and communal living, and then radicalized by Manson's teachings. The group murdered at least nine people, and may have killed as many as twenty-four.

Manson had been institutionalized or incarcerated for more than half of his life by the time he was released from prison in 1967. He began attracting acolytes in the San Francisco Bay Area. They gradually moved to a run-down movie ranch, called the Spahn Ranch, in Los Angeles County. According to group member Susan Atkins, members of the Family became convinced that Manson was a manifestation of Jesus Christ, and believed in his prophecies concerning an imminent, apocalyptic race war.

In 1969, Manson Family members Atkins, Charles Denton "Tex" Watson, and Patricia Krenwinkel entered the home of actress Sharon Tate and murdered her and four others. Linda Kasabian was also present but did not take part. The following night, members of the Family murdered supermarket executive Leno LaBianca and his wife Rosemary at their home in Los Angeles. Members also committed a number of assaults, petty crimes, theft and street vandalism, including an assassination attempt on U.S. president Gerald Ford in 1975 by Family member Lynette "Squeaky" Fromme.

The following is an incomplete list of individuals associated with the Manson Family:

Following his release from prison on March 22, 1967, Charles Manson moved to San Francisco, where, with the help of a prison acquaintance, he moved into an apartment in Berkeley. In prison, bank robber Alvin Karpis had taught Manson to play the steel guitar. Living mostly by begging, Manson soon became acquainted with Mary Brunner, a 23-year-old graduate of the University of Wisconsin–Madison, who was working as a library assistant at the University of California, Berkeley, and moved in with her. According to a second-hand account, Manson overcame Brunner's resistance to him bringing other women in to live with them. Before long, the pair were sharing Brunner's residence with eighteen other women.

Manson established himself as a guru in San Francisco's Haight-Ashbury district, which during 1967's "Summer of Love" was emerging as the signature hippie locale. He may have borrowed some of his philosophy from the Process Church of the Final Judgment, members of which believed Satan would become reconciled to Jesus and they would come together at the end of the world to judge humanity. Manson soon had the first of his groups of followers, most of them female; they were later dubbed the "Manson Family" by Los Angeles prosecutor Vincent Bugliosi and the media. Manson allegedly taught his followers that they were the reincarnation of the original Christians, and that the establishment could be characterized as the Romans. Sometime around 1967, he began using the alias "Charles Willis Manson."

Before the end of summer, Manson and some of his followers began traveling in an old school bus they had adapted, putting colored rugs and pillows in place of the many seats they had removed. They eventually settled in the Los Angeles areas of Topanga Canyon, Malibu and Venice.

In 1967, Brunner became pregnant by Manson. On April 15, 1968, she gave birth to their son, whom she named Valentine Michael, in a condemned house where they were living in Topanga Canyon. She was assisted by several of the young women from the Family. Like most members of the group, Brunner acquired a number of aliases and nicknames, including: "Marioche", "Och", "Mother Mary", "Mary Manson", "Linda Dee Manson" and "Christine Marie Euchts."