Ursula K. Le Guin, the immensely popular author who brought literary depth and a tough-minded feminist sensibility to science fiction and fantasy with books like “The Left Hand of Darkness” and the Earthsea series, died on Monday at her home in Portland, Ore. She was 88.

Her son, Theo Downes-Le Guin, confirmed the death. He did not specify a cause but said she had been in poor health for several months.

Ms. Le Guin embraced the standard themes of her chosen genres: sorcery and dragons, spaceships and planetary conflict. But even when her protagonists are male, they avoid the macho posturing of so many science fiction and fantasy heroes. The conflicts they face are typically rooted in a clash of cultures and resolved more by conciliation and self-sacrifice than by swordplay or space battles.

Her books have been translated into more than 40 languages and have sold millions of copies worldwide. Several, including “The Left Hand of Darkness” — set on a planet where the customary gender distinctions do not apply — have been in print for almost 50 years. The critic Harold Bloom lauded Ms. Le Guin as “a superbly imaginative creator and major stylist” who “has raised fantasy into high literature for our time.”