For 50 years, in movies like “A Man and a Woman” and “My Night at Maud’s,” his specialty was playing the flawed Everyman.Jean-Louis Trintignant, a leading French actor of subtle power who appeared in some of the most celebrated European films of the last 50 years, among them Bernardo Bertolucci’s “The Conformist,” Eric Rohmer’s “My Night at Maud’s” and Claude Lelouch’s “A Man and a Woman,” died on Friday at his home in southern France. He was 91.His wife, Marianne Hoepfner Trintignant, confirmed the death to Agence France-Presse. Mr. Trintignant had announced in 2018 that he had prostate cancer and was retiring.Mr. Trintignant seemed to specialize in playing the flawed Everyman and revealing his characters’ depths slowly.“Jean-Louis Trintignant has been, for better than half a century, one of the great stealth actors of the movies,” the critic Terrence Rafferty wrote in The New York Times in 2012. “He knows how to catch an audience unaware.”The occasion was the release that year of Michael Haneke’s “Amour,” which went on to win the 2013 Academy Award for best foreign-language film. In a starring role for the first time in the millennium, Mr. Trintignant, by then nearly blind, portrayed a frail old man caring for his dying wife, played by Emmanuelle Riva — “two titans of French cinema,” Manohla Dargis wrote in The Times — in a film that is both a love story and a stark examination of illness and mortality.It was the capstone to a rich career playing a gallery of characters who were rarely glamorous. Mr. Trintignant was an emotionally fragile Fascist in “The Conformist” (1970); a timid, meticulous graduate student who accidentally falls in with a ribald bon vivant in Dino Risi’s 1962 “Il Sorpasso” (“The Easy Life”); and a repressed Roman Catholic from the provinces who resists the seductive advances of a beautiful divorced woman in “My Night at Maud’s” (1969).“If some people laugh because I did not have sex with Maud, well, I would prefer being thought ridiculous to being thought a hero,” Mr. Trintignant said in a 1970 interview with The Times. “Even kissing scenes bore me.”In 1969 he won the best actor award at the Cannes Film Festival for his performance as a magistrate investigating the assassination of a Greek politician in Costa-Gavras’s political thriller “Z,” which also won the foreign-language Oscar that year.For American audiences, Mr. Trintignant did not fit the conventional images of French film stars, like the wisecracking Jean-Paul Belmondo, the working-class hero Jean Gabin or the suave sophisticate Maurice Chevalier. He was more understated.“The best actors in the world,” he once said, “are those who feel the most and show the least.”Jean-Louis Xavier Trintignant was born on Dec. 11, 1930, in Piolenc, a small town in southeastern France, where his father, Raoul, was a wealthy industrialist and local politician. Jean-Louis seriously considered becoming a racecar driver like his uncle Maurice Trintignant, a top competitor in the 1950s and ’60s who was only 13 years older than Jean-Louis. (Another uncle, Louis Trintignant, also raced and was killed in 1933 when his car crashed.)Jean-Louis took up law studies instead, thinking he would follow his father into politics. But while a law student in Aix-en-Provence he attended a performance of “The Miser” by Molière and was so smitten that he decided on a stage career.Mr. Trintignant moved to Paris to study acting and began appearing in theater productions at 20. After touring France in the early 1950s, he was hailed as one of the country’s most gifted young stage actors and was soon offered film contracts.Mr. Trintignant with Brigitte Bardot in “And God Created Woman” (1956), directed by Roger Vadim, Ms. Bardot’s husband at the time.Kingsley InternationalIn Roger Vadim’s 1956 movie “And God Created Woman,” Mr. Trintignant starred as a young, naïve husband who is in love with his diabolically flirtatious wife, played by Brigitte Bardot (Mr. Vadim’s wife at the time) in what was considered her breakout sex-kitten role. Whether true or not, rumors circulated that she and Mr. Trintignant had a real-life affair during the filming. Ms. Bardot’s marriage to Mr. Vadim ended in 1957.Mr. Vadim nonetheless cast Mr. Trintignant in the 1959 film “Les Liaisons Dangereuses,” adapted from a sexually scandalous 18th-century novel about a scheming noblewoman. Mr. Trintignant had the lesser but romantic role of the charming Chevalier Danceny, a music teacher for French nobility.The Académie Française, the official arbiter of French culture, denounced the film as “desecrating a classic,” and it was condemned as salacious from Roman Catholic pulpits on both sides of the Atlantic.Mr. Trintignant shared top billing with Vittorio Gassman in “Il Sorpasso,” which is widely considered Mr. Risi’s masterpiece. He played a shy law student who is enticed by Mr. Gassman’s libidinous extrovert and embarks on a rollicking car journey through the Italian countryside that ends tragically.Still more memorable was Mr. Trintignant’s performance eight years laterin “The Conformist.” Based on a novel of the same title by Alberto Moravia, the film is a chilling psychological portrait of a secret policeman in Fascist Italy. Mr. Trintignant, in the lead role, arranges the assassination of his old friend, a left-wing university professor, whose young wife he covets.Mr. Trintignant assumed his most romantic role, as a racecar driver, in “A Man and a Woman” (1966). The movie was an international hit, generating more box-office receipts than any previous French film. He said his early passion for racing — and an intimate knowledge of the sport conveyed to him by his uncles — had made his performance especially credible.But he professed that he was uncomfortable in the movie’s explicit love scenes, in which his co-star was Anouk Aimée, a longtime friend of his wife at the time, the director Nadine Trintignant.“It was embarrassing to find myself in bed with a woman that way,” he told The Times in 1970. “I had known Anouk for 10 years, and she was Nadine’s best friend, and the whole crew was watching.” The movie’s best scenes, Mr. Trintignant insisted, were his hairpin racing turns in Monte Carlo.He went on to appear in an average of three films a year for the next three decades, more often as a supporting actor than as the lead.Mr. Trintignant in “Amour” (2012), which won the Oscar for best foreign-language film. By then nearly blind, he portrayed a frail old man caring for his dying wife, played by Emmanuelle Riva.Sony Pictures ClassicsAn exception was the acclaimed 1994 film “Red,” the finale of the Polish director Krzysztof Kieslowski’s “Three Colors” trilogy. In a work that tracks the parallel lives of a group of people living outside Geneva, Mr. Trintignant played a cold retired judge who spied on his neighbors using high-tech surveillance equipment.He also continued to act onstage occasionally.Later in life Mr. Trintignant returned to his early passion for sports-car racing, participating in the 24 Hours of Le Mans in 1980 and the Monte Carlo Rally in 1984. In the ’90s he spent much of his time tending a vineyard he operated in the South of France or acting in theater. His return to film in “Amour” came after an absence of more than a decade.Mr. Trintignant’s first marriage, to the actress Stéphane Audran, ended in divorce. He married Nadine Marquand, then an actress, in 1960 and had three children with her: Vincent, now a director; Pauline, who died in infancy; and Marie, a successful actress (she had acted alongside her father at age 4 in “Mon Amour, Mon Amour,” which was directed by her mother) and the mother of four who at 41 was beaten to death in her hotel room in Vilnius, Lithuania, in the summer of 2003 while filming there.The murder was a sensation in the European press. Ms. Trintignant’s 39-year-old boyfriend, Bertrand Cantat, one of France’s biggest rock stars, later admitted in a Lithuanian court that he had beaten her in a jealous rage over her plans to vacation with an ex-husband.He was convicted of manslaughter in 2004 and released on parole in 2007, angering the Trintignant family and its supporters.After Marie’s death, Mr. Trintignant fell into a severe depression.“For three months I didn’t speak,” he told the Montreal newspaper The Gazette in 2012. “After that I realized I had to either stop living, commit suicide or continue to live.”In 2011 he withdrew from a planned one-man show at the summer Avignon Festival in France when he learned that Mr. Cantat was to appear at the festival as well in an acting role onstage.Mr. Trintignant’s marriage to Nadine Trintignant ended in divorce in 1976. He married Marianne Hoepfner, a racecar driver, in 2000. Information on other survivors was not immediately available.Mr. Trintignant’s eyesight deteriorated in his later years, but he was accepting of his condition. “We weren’t meant to live more than 80 years,” he told The Gazette. “It’s not so bad as all that. I’m still happy when I’m alone. I have an inner life.”Even at the height of his popularity, Mr. Trintignant insisted that acting was always a struggle.“I am not a born actor,” he said in the 1970 Times interview. “Even today, I am not an instinctive actor. I prepare meticulously, and it is only when I am before the camera that I become completely free.” More