Ray Bradbury, a master of science fiction whose imaginative and lyrical evocations of the future reflected both the optimism and the anxieties of his own postwar America, died on Tuesday in Los Angeles. He was 91.

His death was confirmed by his agent, Michael Congdon.

By many estimations Mr. Bradbury was the writer most responsible for bringing modern science fiction into the literary mainstream. His name would appear near the top of any list of major science fiction writers of the 20th century, beside those of Isaac Asimov, Arthur C. Clarke, Robert A. Heinlein and the Polish author Stanislaw Lem. His books are still being taught in schools, where many a reader has been introduced to them half a century after they first appeared. Many readers have said Mr. Bradbury’s stories fired their own imaginations.

More than eight million copies of his books have been sold in 36 languages. They include the short-story collections “The Martian Chronicles,” “The Illustrated Man” and “The Golden Apples of the Sun,” and the novels “Fahrenheit 451” and “Something Wicked This Way Comes.”

Though none of his works won a Pulitzer Prize, Mr. Bradbury received a Pulitzer citation in 2007 “for his distinguished, prolific and deeply influential career as an unmatched author of science fiction and fantasy.”