After spending much of her childhood in foster homes, Monroe began a career as a model, which led to a film contract in 1946 with Twentieth Century-Fox. Her early film appearances were minor, but her performances in The Asphalt Jungle and All About Eve (both 1950), drew attention. By 1952 she had her first leading role in Don't Bother to Knock and 1953 brought a lead in Niagara, a melodramatic film noir that dwelt on her seductiveness. Her "dumb blonde" persona was used to comic effect in subsequent films such as Gentlemen Prefer Blondes (1953), How to Marry a Millionaire (1953) and The Seven Year Itch (1955). Limited by typecasting, Monroe studied at the Actors Studio to broaden her range. Her dramatic performance in Bus Stop (1956) was hailed by critics and garnered a Golden Globe nomination. Her production company, Marilyn Monroe Productions, released The Prince and the Showgirl (1957), for which she received a BAFTA Award nomination and won a David di Donatello award. She received a Golden Globe Award for her performance in Some Like It Hot (1959). Monroe's last completed film was The Misfits, co-starring Clark Gable with screenplay by her then-husband, Arthur Miller.

Marilyn was a passionate reader, owning four hundred books at the time of her death, and was often photographed with a book.

The final years of Monroe's life were marked by illness, personal problems, and a reputation for unreliability and being difficult to work with. The circumstances of her death, from an overdose of barbiturates, have been the subject of conjecture. Though officially classified as a "probable suicide", the possibility of an accidental overdose, as well as of homicide, have not been ruled out. In 1999, Monroe was ranked as the sixth greatest female star of all time by the American Film Institute. In the decades following her death, she has often been cited as both a pop and a cultural icon as well as the quintessential American sex symbol.