Jerry Lewis, the comedian and filmmaker who was adored by many, disdained by others, but unquestionably a defining figure of American entertainment in the 20th century, died on Sunday morning at his home in Las Vegas. He was 91.

His death was confirmed by his publicist, Candi Cazau.

Mr. Lewis knew success in movies, on television, in nightclubs, on the Broadway stage and in the university lecture hall. His career had its ups and downs, but when it was at its zenith there were few stars any bigger. And he got there remarkably quickly.

Barely out of his teens, he shot to fame shortly after World War II with a nightclub act in which the rakish, imperturbable Dean Martin crooned and the skinny, hyperactive Mr. Lewis capered around the stage, a dangerously volatile id to Mr. Martin’s supremely relaxed ego.

After his break with Mr. Martin in 1956, Mr. Lewis went on to a successful solo career, eventually writing, producing and directing many of his own films.

A mercurial personality who could flip from naked neediness to towering rage, Mr. Lewis seemed to contain multitudes, and he explored all of them. His ultimate object of contemplation was his own contradictory self, and he turned his obsession with fragmentation, discontinuity and the limits of language into a spectacle that enchanted children, disturbed adults and fascinated postmodernist critics.

Jerry Lewis was born on March 16, 1926, in Newark. Most sources, including his 1982 autobiography, “Jerry Lewis: In Person,” give his birth name as Joseph Levitch. But Shawn Levy, author of the exhaustive 1996 biography “King of Comedy: The Life and Art of Jerry Lewis,” unearthed a birth record that gave his first name as Jerome.