Francois Truffaut, the French film director whose personal style of moviemaking revolutionized the cinema, died yesterday of cancer in the American Hospital in Neuilly, a western suburb of Paris. He was 52.

Mr. Truffaut was diagnosed as having a brain tumor in 1983 and went into seclusion. A hospital spokesman said he was admitted 10 days ago and fell into a coma from which he emerged only intermittently.

Constantin Costa-Gavras, head of the prestigious Cinematique Francais, called Mr. Truffaut "irreplaceable. . . . The cinema loses with Francois Truffaut one of its greatest men, who it is not close to replacing."

French Prime Minister Laurent Fabius sent a telegram to Mr. Truffaut's widow, actress Fanny Ardant, saying the director "planted his genius on French cinema for 25 years and made a huge contribution to its rebirth and international influence."

"We have lost a great figure in cinema to whom I wish to pay special homage," Fabius said.

Mr. Truffaut began his career with a splash -- "The 400 Blows," which he directed when he was only 27, won the Golden Palm prize for best film at the Cannes Film Festival, as well as the Academy Award in 1959 for best foreign film. Film producer Ignace Morgenstern, the father of his first wife Madelaine Morgenstern, put up most of the money for "The 400 Blows," despite having been the subject of some of Mr. Truffaut's most vituperative criticism in the French film journal Cahiers du Cinema.

An extraordinarily prolific artist, Mr. Truffaut averaged a film a year over the course of his career, including such classics as "Shoot the Piano Player" (1960), an homage to American gangster movies; "Jules and Jim" (1961), an exploration of an ill-fated menage a trois; "The Wild Child" (1970), which told of a child's conversion from savagery to humanity; "Day for Night" (1973), an examination of the relationship of art to life; "The Story of Adele H." (1975), the story of Victor Hugo's insane, lovesick daughter; "Small Change" (1976), a celebration of the resilience of childhood; and "The Last Metro" (1980), a rallying cry for art for art's sake. His last film was "Decidedly Sunday" (1983).

Mr. Truffaut came to movies as a fan -- he estimated he had seen 3,000 movies by the time he directed "The 400 Blows" -- and as a critic for Andre Bazin's influential journal, Cahiers du Cinema. It was as a critic that he became known as "the demolisher of French cinema" and was banned from Cannes in 1958 for his caustic diatribes against the French film establishment.

Along with his friend and fellow critic/director Jean-Luc Godard, Mr. Truffaut called for an intensely personal kind of film-making -- it was Mr. Truffaut who first defined the "auteur" theory of film-making, which exalted the dominance of the director's individual vision. Together with Godard, Mr. Truffaut fathered what came to be known as the Nouvelle Vague, or New Wave, a blend of documentary-style spontaneity, cinematic adventurousness and American-style narrative verve.

"I don't like specialized cinema," Mr. Truffaut once told an interviewer. "I like popular art. I want my films to be like those I liked as a child."

Mr. Truffaut admired such mainstream directors as Alfred Hitchcock (his book-length interview with Hitchcock, published in 1967, established the director's reputation in Europe), John Ford, and Howard Hawks. He once called Hawks "the greatest cinematic intelligence among American directors. He isn't a cinema addict, nor is he anguished or obsessed. Rather, he loves life in all its manifestations, and because of this harmony with life in general, he was able to make the two or three greatest examples of every genre of film."

Mr. Truffaut in turn influenced such American film-makers as Steven Spielberg, Martin Scorsese, George Lucas, and Brian De Palma, as well as a French school of critic/directors including Jacques Rivette, Claude Chabrol and Eric Rohmer.

"The film of tomorrow appears to me as even more personal than an individual and autobiographical novel, like a confession, or a diary," Mr. Truffaut once wrote. "The young film-makers will express themselves in the first person and will relate what has happened to them . . . and it will be enjoyable because it will be new and true."

Unlike Godard, Mr. Truffaut steered clear of politics; indeed, he was widely criticized for "The Last Metro," set in Vichy France, in which he propounded theatrical excellence as the ultimate value. "I have never admired a politician in my life," he once told an interviewer. "Politicians are like the cleaning lady -- they do their work and get out. I think that to the 20th century, Chaplin is more important than Churchill."

With his indelible Gallic good looks -- a fine straight nose and risible, Gaullois-punctured mouth underneath a noble expanse of forehead -- Mr. Truffaut was a vivid presence in those films, like "Day for Night" and "Wild Child," in which he cast himself, as well as in his role as a French UFO connoisseur in Spielberg's "Close Encounters of the Third Kind."

Born in Paris on Feb. 6, 1932, to an architect and his wife, Mr. Truffaut, unwanted by his parents, was raised by his grandmother until he was 8. His parents took him back after her death but he ran away at the age of 11, and the memories of his lonely, waif-like existence became the material for many of his films.

At the age of 16, he was discovered by Bazin, who became the father he had never had; it was Bazin, for example, who persuaded him to surrender to the authorities after he had deserted from a French regiment destined for Indochina. He was discharged as "an unstable personality" in 1953.

He married Ardant, his leading lady in "The Woman Next Door," and the couple recently had a child, Josephine. He is also survived by two other children, Laura and Eva, by his marriage to Madeleine Morgenstern. Funeral arrangements are incomplete.