Billy Wilder, the caustic writer and director who won six Academy Awards and international acclaim as one of the world's great filmmakers and then spent the last 21 years of his vivid life imploring Hollywood to let him make another movie, died on Wednesday night at his home in Beverly Hills, Calif. He was 95.

He had been suffering from pneumonia, The Associated Press reported.

Almost all the 25 films Mr. Wilder made as a writer-director displayed his slashing wit and stinging social satire. Yet no other major filmmaker slipped so easily into so many genres.

''Double Indemnity'' (1944) defined film noir. ''The Lost Weekend'' (1945), which took the Oscar for best picture and also won Mr. Wilder Academy Awards for director and co-author of the script, is still the most harrowing movie made about an alcoholic. ''Sunset Boulevard'' (1950) is the grandest of melodramas, a corrosive look at an aging silent-film star (Gloria Swanson) and the young screenwriter (William Holden) who becomes her kept man. ''Some Like It Hot'' (1959), with Jack Lemmon and Tony Curtis as hapless musicians who escape gangsters by dressing as women, endures as a great American farce, while ''Sabrina'' (1954) sparkles as a sophisticated romantic comedy in which a chauffeur's daughter (Audrey Hepburn) is wooed by a captain of industry (Humphrey Bogart) and his playboy brother (Holden). And ''Witness for the Prosecution'' (1957), based on an Agatha Christie play, was a powerfully effective courtroom thriller.

Mr. Wilder was among the first of about 1,500 members of the German film industry who fled from Hitler to Hollywood between 1933 and 1939 and transformed American movies. He was one of a few refugees who reached the top of the industry, a feat made more remarkable by his complete inability to speak English when he arrived in Hollywood in 1934.

Mr. Wilder skeptically probed and exposed human weakness, particularly venality and greed. He had an inventive talent for making unpleasant situations hilarious, and he had the courage to deal with traditionally taboo subjects.

Vincent Canby, the longtime chief film critic of The New York Times, once wrote: ''Wilder is often called cynical, mostly, I think, because his movies seldom offer us helpful hints to better lives. There are few people in his movies one could model one's behavior on. He doesn't deal in redeeming social values. Instead, he sees the demeaning ones.''

In Love With Words

Mr. Wilder was a director who protected his scripts. The look of a movie was less important to him than its language. ''I don't like the audience to be aware of camera tricks,'' he told one interviewer. ''Why shoot a scene from a bird's-eye view, or a bug's? It's all done to astonish the bourgeois, to amaze the middle-class critic.''

Those middle-class critics were never quite comfortable with Mr. Wilder's sardonic focus on the dark side of American life. In love with words, he sprinkled sugar laced with acid into movies whose heroes were often adulterers and gigolos. In ''The Apartment'' (1960), an accountant (Lemmon) earns promotions by lending his apartment to executives for their extramarital romps only to fall in love with an elevator operator (Shirley MacLaine) who goes to his apartment for trysts with his boss (Fred MacMurray).

When this morally ambiguous film was named the best picture of 1960, Mr. Wilder became the first person to win three Oscars in a single night -- as director, producer and co-author of the screenplay. (Leo McCarey had had similar success in 1944, when his ''Going My Way'' defeated Mr. Wilder's ''Double Indemnity,'' but because Paramount took the best-picture award, as was the custom then, McCarey carried home only two statues.)

In his private life, Mr. Wilder was abrasive and exuberant, with an impish face and an impertinent irascibility. A small man who was constantly in motion, he was as witty in person as on paper.

His biting one-liners included this definition of an associate producer: ''the only guy who will associate with a producer.''

In postwar Germany, Mr. Wilder was a colonel in the United States Army who oversaw a program that prevented former Nazis from working on films or in the theater. When asked by the director of the traditional Passion play in the town of Oberammergau if a former Nazi, Anton Lang, could play Jesus, Mr. Wilder responded, ''Permission granted, but the nails have to be real.''

Writing in The Times in 1991, Canby called Mr. Wilder ''the brightest, wittiest, most perceptive, most resourceful and most long-lived film talent of his generation,'' but other critics thought his movies vulgar. Still others were troubled by his tendency to pull the sting from the tail of his characters at the last moment, allowing for happy endings. Often, though, those happy endings were ambiguous -- as when the alcoholic writer refuses a drink, at least for the moment, in ''The Lost Weekend.''

Pushing the Boundaries

For two decades -- from the first movie he directed, ''The Major and the Minor'' (1942), to ''Irma La Douce'' (1963) -- Mr. Wilder usually managed to please audiences while creating films whose unsympathetic heroes and black humor were often thought to be at the far edge of what moviegoers would accept. But ''Kiss Me, Stupid'' (1964), a bawdy sex farce with Dean Martin and Kim Novak, seemed to go over that edge; it failed at the box office and was condemned as an occasion of sin by the Roman Catholic Church's Legion of Decency. Mr. Wilder was suddenly out of touch with the audiences that had made him a top director of the 1950's.

Although critics praised some of his later films, like ''The Private Life of Sherlock Holmes'' (1970) and ''Fedora'' (1979), ticket buyers stayed away. Unable to find a studio willing to back his movies after the box-office failure of ''Buddy Buddy'' in 1981, Mr. Wilder spent the rest of his days accepting the lifetime tributes that he called ''Quick, before they croak!'' awards.

He received the Writers Guild Laurel Award in 1980, a tribute from the Film Society of Lincoln Center in 1982, the American Film Institute's Life Achievement Award in 1986 and the Irving Thalberg Award of the Academy of Motion Picture Arts and Sciences in 1987. He had been honored by the Cannes International Film Festival in 1979; at the start of the festival in 1945, ''The Lost Weekend'' had won the top prize, the Palme d'Or.

Mr. Wilder once said that he probably would have traded all the awards for the chance to make one more picture.

With his usual candor, he acknowledged his failures in 1982 when he was saluted at Lincoln Center. ''People say, 'It wasn't your year,' '' he conceded. ''Well, it hasn't been my decade.''

In the 1990's, Andrew Lloyd Webber turned ''Sunset Boulevard'' into a stage musical that most critics felt never approached the magic of the original. ''Sabrina'' was remade in 1995 and failed with critics and audiences. Mr. Wilder looked on with bitter amusement, never at a loss for either words or money.

Roots in Mitteleuropa

Billy Wilder was born Samuel Wilder on June 22, 1906, in Sucha, a village in Galicia, an Austro-Hungarian province that is now part of Poland. His father was Max Wilder, who ran a railway cafe, and his mother was the former Eugenia Baldinger, whose family owned a resort hotel. Recalling his childhood in a big hotel, he remarked, ''I learned many things about human nature -- none of them favorable.''

His mother, who was in love with all things American, nicknamed him Billie in honor of the Buffalo Bill Wild West show. Smart, impudent and undisciplined, he finished high school at the Realgymnasium Juranek for problem students and then, obeying his mother's wishes, entered the University of Vienna as a law student. He lasted three months.

At 18 he found himself a job on a tabloid that put a premium on punchy reporting and celebrity interviews. He was a natural in both areas. In 1926, an interview with Paul Whiteman, the American bandleader, changed Mr. Wilder's life. As a 19-year-old reporter, he became a Vienna tour guide for Whiteman, who took Mr. Wilder to Berlin, where the band was to play.

According to ''Wilder Times,'' a biography by Kevin Lally, Mr. Wilder told his newspaper that he would be back in a few days with an article on the concert. But the Berlin of the Weimar era was the most exciting city east of Paris, and Mr. Wilder had no intention of returning to Vienna.

He wrote freelance articles and was a ghostwriter of silent-movie scripts. For several months he worked as a professional dance partner to rich ladies at the Hotel Eden and then turned the experience into a newspaper series that gave him brief notoriety.

Berlin was filled with talented young men, many of them Jewish writers and filmmakers whom Mr. Wilder would meet again in Hollywood. In 1929, Paul Kohner, who represented Universal Studios in Berlin, and Joe Pasternak, a future MGM producer, gave Mr. Wilder the chance to write a script under his own name. The result, ''Der Teufelsreporter'' (''The Demon Reporter''), was an unmemorable movie about a daredevil reporter.

Mr. Wilder's next movie, ''Menschen am Sonntag'' (''People on Sunday''), was made on a shoestring. Directed by Robert Siodmak from an idea by his younger brother, Curt, the movie, with its unusual neo-Realist style, was a major avant-garde success.

After ''People on Sunday'' (1930), Mr. Wilder and Robert Siodmak were hired by UFA, the top movie studio in Germany. From 1931 to 1933 Mr. Wilder wrote or collaborated on the screenplays of nearly a dozen early sound films.

No Illusions About Hitler

When Hitler came to power in January 1933, the 26-year-old Mr. Wilder fled Germany.

''People said Hitler was a big, loud, unpleasant joke,'' Mr. Wilder once told this reporter. ''But at the UFA building, the MGM of Berlin, the elevator boy was suddenly in a storm trooper's uniform. I had a new Graham-Paige American car and a new apartment furnished in Bauhaus, and I sold everything for a few hundred dollars.''

''A lot of my friends had a fear of going to a country where they didn't speak the language, so they went to Vienna or Prague,'' he continued. ''But anybody who had listened to the speeches knew Hitler would want Austria and the Sudeten part of Czechoslovakia. I was on the train to Paris the day after the Reichstag fire.''

Fluent in French, Mr. Wilder returned to ghostwriting. But he also had a chance to be a co-director, in ''Mauvaise Graine'' (''Bad Seed''). Another shoestring production, it was about a band of young car thieves.

Joe May, a director Mr. Wilder had known at UFA, was by this time producing movies in Hollywood for Columbia. Mr. Wilder sent him a story idea that became his own ticket to Hollywood. ''Pam-Pam'' was a musical about a gang of counterfeiters who masquerade as theatrical producers. Columbia offered a one-way ticket and $150 a week.

Mr. Wilder was met in New York by his brother, Willie, who had come to the United States 12 years earlier. The Wilder brothers were now safe from the Germans; their mother, grandmother and stepfather died in Auschwitz.

Pop song titles were the only English that Mr. Wilder knew. With a translator's help, he wrote a script for ''Pam-Pam.'' Columbia hated it and he was out of a job. He was also out of time. His six-month visitor's visa had almost expired. He could apply for status as an immigrant only at a consulate outside the United States, so he crossed the border to Mexicali. If he couldn't talk his way back into the United States -- and he had almost none of the necessary papers -- he might have to wait years to return.

But words, even in broken English, were Mr. Wilder's genius. He talked the authorities into a visa; later he wrote about those terrifying days in Mexicali in his script for ''Hold Back the Dawn'' (1941), which won him the third of his 12 Oscar nominations as a writer, a record until Woody Allen received his 13th nomination for ''Deconstructing Harry'' (1997). Mr. Wilder's combined nominations for writing, directing and producing total 21 (12 for writing, 8 for directing, and 1 for producing ''The Apartment.'').

Embracing a New Country

As quickly as possible, Mr. Wilder made himself into an American. He avoided the cafes and living rooms where refugees met to drink coffee and speak German. Instead, he lay on the bed in his rented room and listened to the radio and learned 20 new English words every day.

''Most of the refugees had a secret hope that Hitler would be defeated and they could go back home,'' Mr. Wilder said in a 1990 interview. ''I never had that hope. This was home. I had a clear-cut vision: 'This is where I am going to die.' ''

Many of the German-speaking refugees from Hitler -- among them Fritz Lang, Peter Lorre, Otto Preminger and Douglas Sirk -- prospered in Hollywood, but they were actors, directors, producers and composers. Virtually no writer other than Mr. Wilder could scale the language barrier.

But Mr. Wilder never trusted himself to write film scripts on his own. From his arrival in the United States, he wrote with a collaborator. In 1936 Paramount teamed him with Charles Brackett, the conservative, Harvard-educated son of a New York state senator. It was a shotgun marriage made in Hollywood heaven. Over the next 12 years, they wrote 13 screenplays and become the most successful screenwriting team of the 1940's.

Mr. Brackett and Mr. Wilder first collaborated on ''Bluebeard's Eighth Wife'' (1938) for the director who was Wilder's idol, Ernst Lubitsch. The writers' first Academy Award nomination came a year later, for Lubitsch's ''Ninotchka,'' a political satire. They were nominated again for ''Hold Back the Dawn,'' in which Charles Boyer plays a Romanian gigolo stranded in Mexico who marries Olivia de Havilland to get an American visa. Mr. Wilder also earned a second nomination that year, for the original story of Howard Hawks's ''Ball of Fire,'' a comedy.

The partnership was stormy. Maurice Zolotow, in the 1977 biography ''Billy Wilder in Hollywood,'' wrote that the usually dignified Mr. Brackett often hurled the nearest objects at his partner, who ducked them. They parted in 1950.

Mr. Wilder was a difficult partner. Raymond Chandler disliked him so much when they worked together on the screenplay for ''Double Indemnity'' that he tried to get him fired. Collaborators found him insulting, abusive, exhilarating, exasperating and exhausting. One former collaborator, Harry Kurnitz, declared, ''Billy Wilder at work is actually two people -- Mr. Hyde and Mr. Hyde.''

Early on in Hollywood, Mr. Wilder was infuriated by what he considered the butchering of his scripts by the director Mitchell Leisen and talked Paramount into letting him direct a movie of his own. The studio expected that he would make an arty film and fail. Instead, he took aim at the box office with the bright ''The Major and the Minor.'' In the film, Ginger Rogers pretends to be a 12-year-old because she has no money for a full-fare train ticket; Ray Milland is an Army major who, to his discomfort, finds himself falling for a child.

Fluid Identities

Masquerades are among the major themes in Wilder movies. In one of his early German films, ''Ihre Hoheit Befiehlt'' (''Her Highness's Command''), a Bavarian princess disguises herself as a manicurist while the chief of the palace guard pretends to work in a delicatessen. In another, ''Der Falsche Ehemann'' (''The Counterfeit Husband''), twin brothers switch identities. In ''Some Like It Hot,'' men must pretend to be women, and Tony Curtis, wearing women's clothing, shares a bunk with Marilyn Monroe. In Mr. Wilder's second movie as writer-director, ''Five Graves to Cairo'' (1943), the masquerade is deadly. After the British are defeated at the battle of Tobruk, a survivor (Franchot Tone) assumes the identity of a dead waiter at a hotel swarming with German officers. But the waiter was a German spy, and the disguise is doubly dangerous.

Like most of his movies, ''Five Graves to Cairo'' was an adaptation, in this case a radically changed version of a play, ''Hotel Imperial.'' But no matter what his source material, Mr. Wilder almost always transformed it.

Even critics who later accused Mr. Wilder of compromising the acidity of his films with sugar found no fault with the hardness of ''Double Indemnity.'' With a screenplay by Mr. Wilder and Raymond Chandler, the torrid movie has as its romantic leads Barbara Stanwyck as a woman who wants to murder her husband and Fred MacMurray as the insurance salesman who helps her.

It was the sort of antihero role that a half dozen male stars rejected and the kind of morally ambiguous subject that Hollywood's production code considered unsuitable for a movie in 1944, and it won Mr. Wilder the first of eight Oscar nominations as a director. Repeatedly, actors balked at playing Mr. Wilder's morally compromised characters. But Mr. Wilder always did well by his actors, and actors liked him.

''Sunset Boulevard'' -- like ''The Apartment'' and ''Ace in the Hole'' -- was an original screenplay, and Mr. Wilder daringly chose to have the movie narrated by a dead screenwriter who is first seen floating face down in the aging star's swimming pool. ''The opening wasn't logical,'' Mr. Wilder once said, ''but it was riveting. And as long as something is riveting, they will swallow it.'' It was also a typical Wilder device to start a film with voice-over narration.

''Ace in the Hole'' (1951, and also known as ''The Big Carnival''), which followed ''Sunset Boulevard,'' was Mr. Wilder's most savage satire about the greed of American free enterprise. The antihero (Kirk Douglas) is a reporter who uses a man trapped in a cave to create headlines, in the process causing the man's death. ''Americans expected a cocktail and felt I was giving them a shot of vinegar instead,'' Mr. Wilder said. A brilliant film, it was a box-office failure, and Mr. Wilder was careful never to be so downbeat again.

Changing Partners

One reason the partnership of Brackett and Wilder had broken up was because ''Sunset Boulevard'' and ''A Foreign Affair'' (1948), a satire with Marlene Dietrich about opportunistic American officials and G.I.'s in postwar Berlin, were too dark for Mr. Brackett. From ''Ace in the Hole'' on, Mr. Wilder produced his own films.

With ''Love in the Afternoon'' (1957), a May-December romance with Gary Cooper and Audrey Hepburn, he found his second major collaborator, I. A. L. Diamond, who would be the co-writer for his last 12 films, including ''Some Like It Hot;'' ''One, Two, Three'' (1961), a frenetic farce with James Cagney as a Coca-Cola salesman in cold war Berlin; and ''The Fortune Cookie'' (1966), in which Mr. Wilder turned his biting wit on a shady lawyer (Walter Matthau) planning an insurance fraud.

Diamond, who wrote the unforgettable ''Nobody's perfect'' last line in ''Some Like It Hot,'' described his partner's approach to movie making as ''a Middle-European attitude, a combination of cynicism and romanticism.'' The cynicism, he said, ''is sort of disappointed romanticism at heart -- someone once described it as whipped cream that's gotten slightly curdled.''

Other movies directed by Mr. Wilder include ''The Seven Year Itch'' (1955), with its famous moment of Monroe standing over a subway grate, a rush of air from a passing train blowing her dress; ''The Spirit of St. Louis'' (1957), with James Stewart as Charles Lindbergh; and a remake of ''The Front Page'' (1974), with the team of Lemmon and Matthau.

Mr. Wilder married twice. His first marriage, to Judith Iribe, a painter, ended in divorce in 1947. They had one daughter, Victoria. In 1949 he married the former Audrey Young, a singer and actress. He is survived by his wife and daughter.

When he was honored by the Film Society of Lincoln Center in 1982, he refused to be called an auteur. His goal, he insisted in his usual sardonic way, was to have audiences stay awake. ''If you can do it with style, if you can entertain them for two hours and have them talk about the picture for 15 minutes after they leave, I'm satisfied.''