She was born Oona O’Neill on May 14, 1925, in Warwick Parish, Bermuda. Her father was Eugene O’Neill, the playwright who would become one of the most celebrated American dramatists of the twentieth century, the author of Long Day’s Journey into Night, A Moon for the Misbegotten, Mourning Becomes Electra, and The Iceman Cometh. Her mother was Agnes Boulton, a writer whom Eugene O’Neill had married in 1918 and divorced in 1929.
Eugene O’Neill was not a present father. He had separated from Agnes Boulton when Oona was four and had largely disengaged from his children by his second marriage. Oona grew up with her mother, moved in social circles in New York, and became a recognizable face in the emerging postwar culture of young socialites. She appeared on the cover of a magazine. She briefly attempted an acting career.
She met Charlie Chaplin in 1942, when she was seventeen and he was fifty-three. They married on June 16, 1943, in a civil ceremony in Carpinteria, California. She had just turned eighteen. He was fifty-four. The age gap — thirty-six years — caused a scandal that was reported prominently and widely. It was also noted that the marriage was announced approximately two weeks after a paternity suit was filed against Chaplin by Joan Barry, the actress whose case would soon go to trial.
Eugene O’Neill was furious. He disowned his daughter, cut off contact with her and her children, and refused all later attempts at reconciliation. He did not speak to her again before his death in 1953. Oona, for her part, appears to have accepted this estrangement without public recrimination. Her marriage to Chaplin was, by most accounts, solid and enduring. She stayed. When the United States expelled her husband in 1952, she was the one who returned to California to close out their American life. She withdrew their assets, dealt with the property, and made it possible for the family to establish itself in Switzerland.