This is book number 1 in the Hainish Cycle series.
This debut novel from preeminent science fiction writer Ursula Le Guin introduces her brilliant Hainish series, set in a galaxy seeded by the planet Hain with a variety of humanoid species, including that of Earth. Over the centuries, the Hainish colonies have evolved into physically and culturally unique peoples, joined by a League of All Worlds.
Earth-scientist Rocannon has been leading an ethnological survey on a remote world populated by three native races: the cavern-dwelling Gdemiar, the elvish Fiia, and the warrior clan, Liuar. But when the technologically primitive planet is suddenly invaded by a fleet of ships from the stars, rebels against the League of All Worlds, Rocannon is the only survey member left alive. Marooned among alien peoples, he leads the battle to free this newly discovered world and finds that legends grow around him as he fights.