With a handful of like-minded young men, including Isaac Asimov, James Blish, Damon Knight and Mr. Kornbluth, Mr. Pohl threw himself into the burgeoning phenomenon of science fiction fandom. In 1936 he and a dozen other enthusiasts gathered in the back room of a bar in Philadelphia for what many regard as the world’s first science fiction “convention.”

Mr. Pohl’s ambition, like that of his friends, was to be a professional writer. Toward this end he became a literary agent and an editor, both before he was 20. As an agent he represented the work of his friends to the established science fiction magazines; he also published many of their stories, and some of his own, in two new pulp magazines, Astonishing Stories and Super Science Stories, which he edited from 1940 through the summer of 1941.

After serving as an Army weatherman in Italy during World War II, he wrote advertising copy for a mail order publisher. Then he became a literary agent again. In the late 1940s science fiction was becoming respectable, and Mr. Pohl helped connect science fiction writers to mainstream publishers; he sold Mr. Asimov’s first novel, “Pebble in the Sky” (1950), to Doubleday. At the same time, he was writing prolifically, often in collaboration with Mr. Kornbluth. “The Space Merchants” was the most successful of their 11 books together.

In 1960 the British novelist Kingsley Amis hailed Mr. Pohl as science fiction’s “most consistently able writer.” The next year Mr. Pohl began editing two magazines: Galaxy, the monthly that had serialized “The Space Merchants,” and If, in which he introduced a number of important new writers, including Larry Niven and Alexei Panshin. Under his leadership, If won the Hugo — an award voted by science fiction fans — for best magazine in 1966, 1967 and 1968.

After 1969, Mr. Pohl devoted most of his energies to writing. Yet he also found time to serve as science fiction editor at Bantam Books in the mid-’70s. It was a period of creative turmoil in science fiction, when a group of writers known as the New Wave sought to elevate genre writing by emphasizing literary style and character development. At Mr. Pohl’s urging, Bantam published two of the most important science fiction books of the era: “The Female Man,” by Joanna Russ, a feminist novel in which the war between the sexes is fought with real bullets; and “Dhalgren,” by Samuel R. Delany, a vast experimental work that owed as much to James Joyce as to H. G. Wells. Although the book met resistance at first from the Bantam sales force, “Dhalgren” went on to sell more than a million copies.

The ’70s also saw the blossoming of Mr. Pohl’s own writing career. In 1976 he won his first Nebula Award, given by the group now known as the Science Fiction and Fantasy Writers of America, for “Man Plus,” about an astronaut whose body is surgically altered for life on Mars. He won another Nebula in 1977 — and a Hugo in 1978 — for “Gateway,” which he considered his best novel. It told the story of a man who gains a fortune but loses the love of his life on a “prospecting” expedition aboard an alien spaceship, one of many left behind by the mysterious Heechee, who have taken refuge from even more mysterious aliens inside a black hole. Its most memorable character was a robot psychiatrist who tries to help the hero come to terms with his survivor’s guilt. He wrote four more novels and a book of short stories in the Heechee saga.