Tallulah Willis

Moore was born November 11, 1962, in Roswell, New Mexico. Her biological father, Air Force airman Charles Foster Harmon Sr., deserted her then-18-year-old mother, Virginia (née King), after a two-month marriage before Moore's birth. Charles came from Lanett, Alabama, and Virginia was born in Richmond, California but had grown up in Roswell. Moore's maternal grandmother was raised on a farm in Elida, New Mexico. Moore has deep roots in the South Central and Southern United States, particularly Oklahoma, Arkansas and Georgia. When Moore was three months old, her mother married Dan Guynes, a newspaper advertising salesman who frequently changed jobs; as a result, the family moved many times. In 1967 they had Moore's half-brother Morgan. Moore said in 1991, "My dad is Dan Guynes. He raised me. There is a man who would be considered my biological father who I don't really have a relationship with." Moore has half-siblings from Charlie Harmon's other marriages, but she does not keep in touch with them either.

Moore's stepfather Dan Guynes married and divorced Virginia twice. On October 20, 1980, a year after their second divorce from each other, Guynes committed suicide. Her biological father Harmon died in 1997 from liver cancer in Brazoria, Texas. Moore's mother had a long arrest record which included drunk driving and arson. Moore broke off contact with her in 1989, when Guynes walked away halfway through a rehab stay Moore had financed at the Hazelden Foundation in Minnesota. Virginia Guynes posed nude for the magazine High Society in 1993, where she spoofed Moore's Vanity Fair pregnancy and bodypaint covers and parodied her clay scene from Ghost. Moore and Guynes reconciled shortly before Guynes died of a brain tumor on July 2, 1998.

Moore spent her early childhood in Roswell, and later, Canonsburg, Pennsylvania. Bob Gardner, a photographer for the Monongahela Daily Herald when Dan Guynes was head of advertising, recalled that Moore "looked malnourished and not so much abused as neglected. That haunting look as a child made me feel uneasy." She suffered from strabismus, which was corrected by two operations, as well as kidney dysfunction. Moore learned that Guynes was not her real father at age 13, when she discovered a marriage certificate and inquired about the circumstances since she "saw my parents were married in February 1963. I was born in '62."

At age 14, Moore returned to her hometown of Roswell and lived with her grandmother for six months before relocating to Washington state, where her recently separated mother was residing near Seattle. Several months later, the family moved again to West Hollywood, California, where Moore's mother took a job working for a magazine distribution company. Moore attended Fairfax High School there. In 2019, she stated she was raped at 15 by landlord Basil Doumas, then 49. Doumas claimed he had paid Moore's mother to get access to Moore to rape her, although Moore said it is unclear if this were true.

In November 1978, Moore moved in with 28-year-old guitarist Tom Dunston, quitting high school in her junior year to work as a receptionist at 20th Century Fox—a job she secured through Dunston's mother, who was an executive assistant to producer Douglas S. Cramer. She signed with the Elite Modeling Agency, then enrolled in acting classes after being inspired by her next-door neighbor, 17-year-old German starlet Nastassja Kinski. In August 1979, three months before her 17th birthday, Moore met married musician Freddy Moore, at the time leader of the band Boy, at the Los Angeles nightclub The Troubadour. He obtained a divorce in late 1980 and married Demi six weeks later.