Seberg was born in born in Marshalltown, Iowa. She was discovered by Otto Preminger, who directed her in her first two films. She would go on to star in 34 films in Hollywood and in France where she lived in Paris with her first husband, attorney François Moreuil. She became even more of an icon from her roles in numerous French films and the tragedy of her turbulent life. Among her roles, she co-starred with Jean-Paul Belmondo in Jean-Luc Godard's classic work of New Wave cinema, Breathless (original French title: A bout de souffle).

During the latter part of the 1960s, Seberg used her high-profile image to voice support for the NAACP and supported Native American school groups such as the Mesquakie Bucks at the Tama settlement near her home town of Marshalltown, for whom she purchased $500 worth of basketball uniforms. She also supported the Black Panther Party. FBI director J. Edgar Hoover considered her a threat and in 1970, when she was seven months pregnant, allegedly created a story to leak to the media that the child she was carrying was not fathered by her second husband, Romain Gary, but by a black civil rights activist. The story was reported by Joyce Haber of the Los Angeles Times newspaper, and Newsweek magazine. She miscarried shortly thereafter. In a press conference after the miscarriage she presented the press with a picture of her fetus to demonstrate that the child did not have a father of African heritage. Seberg stated that the trauma of this event brought on premature labor and her child was stillborn. According to her husband, after the loss of their child she suffered from a deep depression and became suicidal. She also became dependant on alcohol and prescription drugs. She made several attempts to take her own life, including throwing herself under a train on the Paris Métro.

Seberg's problems were compounded when she went through a form of marriage to an Algerian playboy, Ahmed Hasni, on May 31, 1979. The brief ceremony had no legal force because she had taken film director Dennis Berry as her third husband in 1972 and the marriage was still valid. In July, Hasni persuaded her to sell her opulent apartment on the Rue du Bac, and he kept the proceeds (reportedly 11 million francs in cash), announcing that he would use the money to open a Barcelona restaurant. The couple departed for Spain but she was soon back in Paris alone, and went into hiding from Hasni, who she said had grievously abused her.

In August 1979, she went missing, and was found dead 11 days later in the back seat of her car in a Paris suburb. The police report stated that she had taken a massive overdose of barbiturates and alcohol (8g per litre). A suicide note ("Forgive me. I can no longer live with my nerves") was found in her hand, and suicide was ultimately ruled the official cause of death. However, it is often questioned how she could have driven to the address in the 16th arrondissement with that amount of alcohol in her body, and without the distance glasses she always maintained she absolutely needed for driving.

Seberg was interred in the Cimetière du Montparnasse, Paris, France.