Anne McCaffrey, a science-fiction writer widely known as the Dragon Lady for her best-selling series of young-adult novels, “Dragonriders of Pern,” died on Monday in County Wicklow, Ireland. She was 85.

The cause was a stroke, her publisher, Random House, told The Associated Press. Ms. McCaffrey, who had lived in Ireland since the 1970s, died at her home, Dragonhold — so named, she liked to say, because it had been paid for by dragons.

The author of scores of books in a spate of different series, Ms. McCaffrey was indisputably best known for “Dragonriders,” written over four decades and comprising more than 20 novels.

That series, which is notable for marrying elements of fantasy to pure science fiction, takes place on the planet Pern, which Earthlings have settled. A utopian idyll at first, Pern has degenerated, after centuries of human habitation, into a tense feudal society.