When Ingrid Bergman accepted an Oscar for best supporting actress in 1975 for her cameo role in “Murder on the Orient Express,” she stood before millions of television viewers and insisted that fellow nominee Valentina Cortese was more deserving of the prize.

Bergman later conceded the impolitic nature of her remark, given the presence of the other losing actresses — Madeline Kahn, Diane Ladd and Talia Shire. But she said she felt compelled to highlight Ms. Cortese’s bravura and heavily improvised portrayal of an aging, alcoholic movie star in “Day for Night,” the Oscar-winning French-language romantic comedy by writer-director François Truffaut.

“She gave the most beautiful performance,” Bergman declared of Ms. Cortese at the Academy Awards ceremony. “Please forgive me, Valentina.”

Ms. Cortese’s humane portrait, equal parts comic and disturbing, captured a prima donna past her prime and on the verge of a breakdown. Her character blows her lines, opens the wrong doors and weeps in the arms of a clearly uncomfortable younger lover. “As soon as we grasp things,” says the champagne-tippling Séverine, unmoored by her faulty memory, “they’re gone.”

Ms. Cortese, who appeared in more than 100 movies and TV shows under directors as varied as Robert Wise, Jules Dassin, Terry Gilliam and Federico Fellini, died July 10 in Milan at 96. Mayor Giuseppe “Beppe” Sala announced the death in a tweet but did not provide a cause.

With her headscarves and unguardedly discursive style — she peppered her conversations with the endearment “darling” — Ms. Cortese cut a flamboyant profile in Hollywood, if only briefly, and in the filmmaking capitals of Europe for more than five decades. Her performances combined wily intelligence and earthy sensuality, and she was esteemed among her peers and by some critics. But she never attained top stardom, a reflection of her self-described “nonconformist” attitude toward the star­making machinery.

Valentina Cortese in 1949. (AP)

“If I wanted to be a star, I would have guided it,” she once told the New York Times. “I had all the cards. Sophia Loren is Sophia Loren because Carlo Ponti directed her in a certain way. Silvana Mangano is where she is because of Dino De Laurentiis. But I’m in rebellion. For me, the greatest richness for an actor, rather than to go up, up, up, up and own villas and yachts, is that moment when he’s there on the set or on stage, and he gives something — a message of love or of life — to his own public, and he does it with truth.”

Ms. Cortese entered films in 1941 playing ingenues before portraying two female lead characters, Fantine and Cosette (mother and daughter), in a 1948 Italian adaptation of the Victor Hugo novel “Les Misérables.” She went to England the next year to make a romantic melodrama, “The Glass Mountain,” a hit that captured the attention of Darryl F. Zanuck, chief of Twentieth Century Fox studios.

He signed her to a contract, changed the spelling of her name to Cortesa and showcased her in a series of dramas — placing her in the vanguard of Italian actresses lured to Hollywood after World War II, among them Anna Magnani, Gina Lollobrigida and Loren.

Perhaps Ms. Cortese’s finest early turn was in Dassin’s well-regarded film noir “Thieves’ Highway” (1949), in which she played a streetwalker who helps a handsome young truck driver (Richard Conte) take down a corrupt San Francisco produce dealer (Lee J. Cobb).

On loan to Metro-Goldwyn-Mayer studios, she portrayed an Italian torch singer in “Malaya” (1949), a World War II film with James Stewart and Spencer Tracy that bombed at the box office.

Ms. Cortese then starred in Wise’s “The House on Telegraph Hill” (1951) as a Polish woman who survives a Nazi concentration camp, steals a dead friend’s identity, moves to San Francisco and lands in a nest of vipers scheming after a fortune. She married her co-star, Richard Basehart.

“Hollywood was very beautiful, like a set built up to be destroyed the next day,” she later told the Times. “It was a lovely life, full of sunshine and swimming pools. But I need to walk and have a feeling of human beings around, and you don’t have that there.”

She soon returned to Italy, where Basehart starred in Fellini’s 1954 masterpiece, “La Strada,” and Ms. Cortese had a supporting role the same year in “The Barefoot Contessa,” director Joseph L. Mankiewicz’s shaggy dog satire of the film business starring Humphrey Bogart and Ava Gardner.

Ms. Cortese went on to a long and periodically distinguished career in European cinema, including Michelangelo Antonioni’s “Le Amiche” (1955) as a ceramic artist with a masochistic devotion to her philandering husband, Fellini’s surrealistic “Juliet of the Spirits” (1965) and Franco Zeffirelli’s TV miniseries “Jesus of Nazareth” (1977) as the princess Herodias.

The centerpiece of her later career was “Day for Night.” The film, about the backstage personalities on a movie set, was partly anchored by what Times movie critic Vincent Canby called Ms. Cortese’s “hugely funny but also hugely affecting” portrayal.

She also was a stalwart of Milan’s Piccolo Teatro, working frequently under Zeffirelli (notably in the Friedrich Schiller verse play “Mary Stuart”) and Giorgio Strehler.

Valentina Cortese was born in Milan to an unmarried concert pianist on Jan. 1, 1923. She said she was deposited with foster parents in rural Lombardy and spoke with happiness about her upbringing there.

“I am always saved by this good base in life, this peasant reality,” she told the Times. “I’m not at ease to go around in a Rolls-Royce. I’ve always thought that if a rich man falls in love with me, he should stay away from me, because I would give all his money away.”

She began performing at 15 at open-air village festivals on the banks of Lake Maggiore and was spotted by theater critics from Milan newspapers who encouraged her to take the entrance exam for the national academy of dramatic arts in Rome.

One of the examiners was a prominent Italian film director who signed her on the spot. She said she became so busy in movies that she never had time to study at the academy.

Off-screen, she began a long-term affair with Victor de Sabata, a married Italian conductor and composer three decades her senior. She left for Hollywood in large part to break off their intense relationship, and she soon had a romantic fling with Dassin. (“One evening he asked me: ‘Would you mind if I fell in love with you?’ ”)

Her marriage to Basehart ended in divorce. As she later told an Italian publication: “He wanted to go back to Hollywood. I stayed in Italy. We parted. I discovered that he had also betrayed me with the babysitter.” Their son, Jackie, who became an actor, died in 2015. She was predeceased by her second husband, pharmaceuticals magnate Carlo de Angeli. A list of survivors was not immediately available.

Ms. Cortese’s films included “Secret People” (1952), a political thriller featuring a young Audrey Hepburn, and “Love and Troubles” (1958), an Italian comedy with Basehart and Marcello Mastroianni. In director Joseph Losey’s “The Assassination of Trotsky” (1972), she won admiring reviews in the small role of the wife of exiled Russian Revolution leader Leon Trotsky (played by Richard Burton). She was the lunar queen in Gilliam’s “The Adventures of Baron Munchausen” (1988).

Francesco Patierno used eight actresses to portray dimensions of her life in “Diva!,” a 2017 documentary based on her memoir, “Quanti Sono I Domani Passati” (“How many tomorrows past”).

“People go to the movies to see beautiful young girls, but an older woman who has worked a long time has achieved something a young actress hasn’t,” she told the Times in 1974. “I don’t have ambitions. I just love what I do. How could I have become like Sophia Loren, where Ponti builds her and she says, ‘Yes, yes, yes.’ I’m free to make my own mistakes. And at least I am myself.”