Gardner R. Dozois, 70, one of the most important science-fiction editors of his time, died Sunday, May 27, at Pennsylvania Hospital of multiple system failure.

Mr. Dozois, a member of the Science Fiction and Fantasy Hall of Fame, was the founding editor of The Year's Best Science Fiction anthologies and a longtime editor of Asimov's Science Fiction magazine. He earned dozens of awards for his work, both as a writer and an editor.

What drove Mr. Dozois was a desire to find and publish the best of the genre, said a friend, the science-fiction author Michael Swanwick.

"He loves science fiction with an intensity that very few can match," Swanwick wrote about Mr. Dozois in 1997.

Born in Beverly, Mass., Mr. Dozois became an avid fiction reader in part, he told friends, as a way to escape small-town life. Even as a young child, he was focused on fantasy, interested in becoming a writer someday. After graduating from high school in 1965, he served in the Army, working as a journalist for Stars and Stripes, the military newspaper, from 1966 to 1969. He received no further formal education beyond high school, but was a voracious reader and once landed on a Philadelphia Magazine list of the 100 smartest people in the city.

Mr. Dozois moved to New York when he left the military, launching a career he would pursue for the rest of his life. At first, he was a celebrated young writer of short stories, but then he began to get work as an editor, and quickly got a reputation as a very strong one.

He moved to Philadelphia in 1970 when he fell in love with Susan Casper, whom he would go on to marry. Casper was his collaborator in life and often in writing; she was also a science-fiction author. He lived in the city for the rest of his life — in Society Hill and then in Fairmount.

In the 1970s, Mr. Dozois worked on a number of science-fiction magazines. From 1988 to 2004, he edited Asimov's Science Fiction; during that time, he won the Hugo Award for Best Professional Editor, a prize given by the World Science Fiction Society.

He considered himself a writer's editor: "Rather than telling my writers what to write about or giving them ideas, I prefer to stay as receptive as I can to the areas they're interested in exploring," Mr Dozois said in a 1999 interview. He was a careful and generous mentor, friends said, and loved widening the genre and finding new voices.

Mr. Dozois was also an anthologist, choosing the best science-fiction work annually for The Year's Best Science Fiction, a work published for the last 35 years. The stories he chose were acclaimed, winning a legion of prizes on the national and international stages.

He frequently worked with others in the industry — from Swanwick and his wife to George R. R. Martin, the writer responsible for Game of Thrones.

Though Mr. Dozois spent most of his time reading other writers' work, he still managed to write his own, including "The Peacemaker" and "Morning Child," which each won Nebula Prizes as best short stories; the novel Strangers; and Hunter's Run a novel written in collaboration with George R. R. Martin and Daniel Abraham. After his wife died in 2017, Mr. Dozois used writing as a way to cope with his grief; he produced five new stories after her death, said his son, Christopher Casper.

Mr. Dozois came across as larger-than-life, gregarious, and colorful. But he was layered, his son said. He was accomplished — Casper accepted a lifetime achievement award on his father's behalf from the Science Fiction and Fantasy Writers of America this month — but uncomfortable with praise.

"He used humor as his own personal shield to help put people at ease," said Casper. "Considering all he had done, he was a shy and humble man."

Despite his prominence in the industry, Mr. Dozois was never wealthy. But he was generous, always.

"Even when he turned down stories, it was always with a kind heart — it was never just, 'No.' He gave writers feedback to make their work better. And if he passed a homeless gentleman on the street, he would always give them a dollar if he had it in his pocket," said Casper. "He always thought to give."

Asked once what inspired him as a writer, Mr. Dozois in a 2010 interview said that he "wanted to write the stories I wanted to read.  Everybody has a unique view of the universe, a view that can be seen only through their eyes, and nothing quite matched the view from my own eyes."

Survivors include his son, two grandchildren, and a sister, Gail Fennessey.

A memorial service is being planned for July.