Born January 7, 1929, in Glendale, California, as Helen Luella Koford, Moore grew up in a Mormon family in Los Angeles, California. She worked as a child model before making her film debut in Maryland in 1940. Moore was billed as Judy Ford, Jan Ford, and January Ford before taking Terry Moore as her name in 1948.
Moore worked in radio in the 1940s, most memorably as Bumps Smith on The Smiths of Hollywood. She has starred in several box-office hits, including Mighty Joe Young (1949), Come Back, Little Sheba (1952) (for which she was nominated for an Academy Award for Best Supporting Actress), and Peyton Place (1957). She appeared on the cover of Life magazine for July 6, 1953, as "Hollywood's sexy tomboy". Moore's photo was used on the cover of the second issue of the My Diary romance comic book (cover dated March 1950).
During the 1950s, Moore worked steadily in films such as The Great Rupert (1950), Two of a Kind (1951), Man on a Tightrope (1953), Daddy Long Legs (1955), Between Heaven and Hell (1956), Bernardine (1957), A Private's Affair (1959) and Why Must I Die? (1960).
By the 1960s, Moore's film career had faltered. She had begun to appear less frequently in films. However, she did make films such as Platinum High School (1960), She Should Have Stayed in Bed (1963), Black Spurs (1965), Town Tamer (1965), Waco (1966) and A Man Called Dagger (1967). Lacking film roles, Moore appeared on television. In 1962, she appeared as a rancher's daughter in the NBC Western Empire. She also appeared on the NBC interview program Here's Hollywood.
After the 1960s, Moore semiretired from acting, only completing two films in the 1970s; by the 1980s, though, her career had resumed with minor roles in low-budgeted B-movies. Moore has a star on the Hollywood Walk of Fame at 7080 Hollywood Blvd.
At age 55, Moore posed nude in the August 1984 issue of Playboy magazine, photographed by Ken Marcus. In 2014, she guest-starred in the role of Lilly Hill on the crime series True Detective, starring Matthew McConaughey.
Moore's first marriage, in 1951 to American football player and Heisman Trophy winner Glenn Davis (known as Mr. Outside when he played at the U.S. Military Academy at West Point), lasted one year. A subsequent marriage to Eugene McGarth, in 1956, lasted three years. One year after this marriage ended, Moore married Stuart Cramer after his divorce from Jean Peters; one of the two children from this 13-year marriage is actor Grant Cramer. Following the dissolution of this marriage in 1972, Moore did not remarry for 20 years. Her 1992 marriage to Jerry Rivers lasted until his death in 2001.
Moore became the subject of public attention as a result of her relationship with Howard Hughes. According to Moore, she and Hughes were married in 1949 in a ceremony performed by a ship captain in international waters. Moore has said that Hughes destroyed the ship's log that recorded the marriage, and they separated from each other by 1956, but she and Hughes were never divorced. Moore has explained her subsequent marriages during Hughes' lifetime by saying, "I didn't care whether I was a bigamist or not, frankly. I mean, my desire to have children was that strong."
The Texas courts rejected Moore's claim of being Hughes' widow based on judicial estoppel; since Moore had claimed in her divorce from Cramer to have been married to him in 1959 and received a property settlement in that case, her claim that she was married to Hughes at the time was inconsistent with that and would not be accepted. Nevertheless, the Hughes heirs agreed that Moore had had a long-term relationship with Hughes and agreed to a financial settlement with her. Moore described the settlement as "not more than eight figures", although a biography of Hughes implies that the settlement was $350,000.