While in high school in 1972, she was raped and became pregnant. Her illegal abortion paved the way for France to decriminalize the procedure in 1975.Marie-Claire Chevalier was 16 when she was raped by a high school classmate and became pregnant. She then had an abortion, which was illegal at the time unless the woman’s life was in danger.Her classmate was later arrested on unrelated charges of auto theft. In a bid to avoid prosecution, he revealed Ms. Chevalier’s abortion to the authorities; he was released, and she was arrested and imprisoned.In a sensational 1972 trial, she was represented by Gisèle Halimi, one of Frances’s most renowned lawyers and a prominent feminist. She won Ms. Chevalier’s acquittal, and the landmark case helped pave the way for the decriminalization of abortion in France.While many in France celebrated the outcome, Ms. Chevalier was traumatized by the whole experience. She changed her first name to Catherine after the trial to try to regain her anonymity and lived the rest of her life out of the public eye.Ms. Chevalier died on Jan. 23 in a hospital in Orléans, south of Paris. She was 66. The cause was brain cancer, her mother, Michèle Chevalier, said.In predominantly Roman Catholic France, abortion was long considered a mortal sin and was officially banned by the Napoleonic Code of 1810, which threatened women who had abortions with imprisonment. During the German occupation in World War II, the procedure was deemed a capital crime, and some women who underwent abortions or performed them were executed, often by guillotine. The last such execution was in 1943.By the late 1960s and early ’70s, a series of legal challenges focused increasing attention on the abortion statute. Perhaps the most prominent of these challenges was that of Ms. Chevalier, whose mother had sought out Ms. Halimi to represent her.Ms. Halimi agreed to do so with the goal of politicizing the case and legalizing abortion. Some of France’s leading intellectuals, including Simone de Beauvoir, joined the cause.The trial took place in the Paris suburb of Bobigny when Ms. Chevalier was 17. Ms. Halimi declared in her opening argument that she, too, had had an abortion. “I say it gentlemen, I am a lawyer who broke the law,” she declared in court. She received a disciplinary summons but maintained in subsequent appearances that she had done the right thing, saying, “Sometimes it is necessary to break the law to move forward and bring about a change in society.”When the verdict was rendered, Ms. Chevalier was fined 500 francs and released, while activists chanted her name in the streets. Four others, including her mother, had been charged as accomplices and were absolved.The case, with its young protagonist and its high-profile lawyer, became a cause célèbre and a catalyst in the feminist campaign to overturn the law. Among those who joined was Simone Veil, the French health minister and a survivor of Auschwitz. She endured an avalanche of personal attacks but kept pushing for change. And on Jan. 17, 1975, France enacted the Veil Law, decriminalizing abortion.This was two years after the U.S. Supreme Court had legalized abortion in the United States Roe v. Wade. As in France, it had taken another pregnant woman, a Dallas waitress named Norma McCorvey — under the pseudonym “Jane Roe” — to challenge the law and achieve a major victory for women.Although Ms. Chevalier was proud of the effect her case had had, she loathed the publicity and shunned the notion of exploiting it for fame or profit. “It’s not my style to build on what has screwed me up,” she said in a rare interview in 2019 with the French newspaper “Libération.”Still, her story has been packaged and repackaged for public consumption by the media, in a radio series, a television movie and theatrical productions, including a play in 2019 at the Comédie-Française, called “Hors la Loi” (“Outlaw”). A blue metal footbridge in front of the Bobigny court was dedicated in her name.But she remained haunted by the experience, from the rape and abortion to the trial.“Time has passed, and yet it’s still there, buried in my memory,” she said in the 2019 interview. “All it takes is a tiny little thing to wake it up.”Marie-Claire Chevalier was born on July 12, 1955, into a working-class family in Meung-sur-Loire, near Orléans.Her father was never part of the picture. Her mother, who was a ticket inspector for the RATP, the state-owned transportation company, raised her and her two younger sisters by herself.In the 2019 interview, Ms. Chevalier described her clandestine abortion as “a second rape,” a gruesome and painful procedure that she said led to her hemorrhaging and being rushed to a hospital, near death.She was in her 30s before she had sex again, she said. But she and her partner could not conceive, and she worried that the abortion had made her sterile. In 1988, she finally had a daughter.In addition to her mother, she is survived by her daughter, three grandchildren and her two sisters.She later worked as a child-care assistant and as a welder for the army. When she was about 40, she became a nurse, working in a hospital and a retirement home. In her final years, she lived alone with her many cats and two horses in the countryside.“She died without ever asking anyone for anything,” her mother said in an interview. “She needed help, and she never contacted us.”But she remains an inspiration to younger French feminists.“Marie-Claire Chevalier has made us the most beautiful gift,” Céline Piques, the spokeswoman for “Osez le féminisme!” (“Dare to be feminist!”), said in an interview. That gift, she said, was to take on the cause of abortion rights “and to agree to be publicly exposed, with the consequences I assume it had on her personal life.”