Bernadette Lafont, who has died aged 74, could have claimed to be the first female star of the Nouvelle Vague. François Truffaut chose the sensual, dark-haired, 18-year-old Lafont and her new husband, Gérard Blain, to play lovers in the director's first professional film, Les Mistons (The Mischief-Makers, 1957). In this charming short, shot in Nîmes one summer, a group of pubescent boys spy on Lafont and Blain's lovemaking in the fields. Blain and Lafont were also picked to appear in arguably the first French New Wave feature, Claude Chabrol's Le Beau Serge (1958). In this film, about a young man returning to his childhood home, Lafont played the "village vamp".

Lafont's fresh look and performance style crystallised the movement's ideological and cinematic ambitions. Truffaut and his colleagues found mainstream stars inadequate to their needs, using instead unknown and non-professional actors, and in doing so creating their own stars. The acting of Lafont, Blain, Jean-Claude Brialy, Jean-Paul Belmondo and Jean-Pierre Léaud was a marked departure from much that had gone before. They were encouraged to improvise or talk over each other's lines as would happen in real life.

Lafont had joie de vivre, spontaneity and a rebellious streak. Truffaut, who called her a "wild child", later exploited her vitality in Une Belle Fille Comme Moi (A Gorgeous Girl Like Me, 1972), in which she played a murderer who frankly tells a criminologist about her sexual relationships. It seemed surprising that she was then the former character in La Maman et la Putain (The Mother and the Whore, 1973), Jean Eustache's long, erotic, witty and provocative ménage-à-trois film essay, which might be described as the summation of the French New Wave. As a businesswoman, supporting Léaud, she delivers uncompromising sexual admissions directly to camera in a natural manner that continues to astonish.

Born in Nîmes, southern France, Lafont was the daughter of a Protestant chemist and a Catholic mother. Her mother had wanted a boy and always called her "Bernard". Lafont took ballet lessons, and appeared in performances as a teenager at the Nîmes Opera House.

She believed that her training as a dancer helped her move with ease on screen. Truffaut saw immediately that she was "instinctively at home in front of the camera".

After Le Beau Serge, Chabrol cast her in A Double Tour (Web of Passion, 1959), a murder mystery in which Lafont is a wilful young woman who introduces her uncouth boyfriend (Belmondo) to her bourgeois family. This was followed by Chabrol's early masterpiece Les Bonnes Femmes (1960), in which she is superb as a fun-loving but vulnerable shop girl. In Chabrol's Les Godelureaux (Wise Guys, 1961), one of his most anarchic films, Lafont mischievously makes a play for a man in front of her boyfriend.

In 1969, her extrovert talents were given free rein in La Fiancée du Pirate (A Very Curious Girl), Nelly Kaplan's social satire. In the plot, after her mother is killed in a hit-and-run accident, Lafont takes revenge on the citizens of the village who have treated her with scorn. She is brilliant in her transformation from the sloppy despised servant girl to a seductive woman.

Lafont then entered what she called her "experimental period", appearing in Jacques Rivette's mysterious tales Out 1 (1971) and Noroît (1976), for which her mixture of the earthy and the ethereal was well suited. Along with Catherine Deneuve and Agnès Varda, among scores of women in the public eye, she signed the 1971 "Manifesto of the 343" declaring that she had had an abortion voluntarily. The manifesto freed up the laws that governed abortion in France.

Seldom out of the public eye, Lafont continued to bring her forceful persona to bear on both commercial and "art" films and on television. In 1985, she won a César award for her role as the perceptive housekeeper to the teenaged Charlotte Gainsbourg in Claude Miller's L'Effrontée (The Impudent Girl); Miller had been a protégé of Truffaut. Still faithful to the New Wave directors who launched her career, Lafont then appeared as an enigmatic widow in Chabrol's Inspecteur Lavardin (1986).

By then, she and Blain had divorced and Lafont had married the sculptor and director Diourka Medveczky, with whom she had three children. Their daughter Pauline, an actor, died in a climbing accident in 1988. Lafont took "refuge and consolation" in the theatre. She appeared in plays by Sacha Guitry and Marcel Pagnol, and in The Vagina Monologues. In Julie Delpy's film Le Skylab (2011), she was as attractive and expansive as ever as a grandmother at a family gathering. One of her last appearances was in the hugely successful Paulette (2012), as a drug-dealing widow, still insolent after all those years.

She is survived by her son, David, and her daughter Elisabeth.

• Bernadette Lafont, actor, born 28 October 1938; died 25 July 2013

Ronald Bergan
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