Earthsea is a fictional world created by American writer Ursula K. Le Guin. Introduced in her short story "The Word of Unbinding", published in 1964, Earthsea became the setting for six Earthsea books, beginning with A Wizard of Earthsea, first published in 1968, and continuing with The Tombs of Atuan, The Farthest Shore, Tehanu, Tales from Earthsea and The Other Wind. Nine short stories by Le Guin are set in Earthsea; the earliest two ('"The Word of Unbinding'" and "The Rule of Names") in her 1975 collection of short stories The Wind's Twelve Quarters, five in Tales from Earthsea, and the final two (2014's '"The Daughter of Odren'" and 2018's "Firelight") in an illustrated collection (along with the 1993 essay Earthsea Revisioned) in The Books of Earthsea (released in 2018 to celebrate the 50th anniversary of A Wizard of Earthsea).

The world of Earthsea is one of sea and islands: a vast archipelago of hundreds of islands surrounded by mostly uncharted ocean. Earthsea contains no large continents, with the archipelago resembling Indonesia or the Philippines. The largest island, Havnor, at approximately 380 miles (610 km) across is about the size of Great Britain. The cultures of Earthsea are not direct analogues of those of our world, but are literate non-industrial civilizations. Technologically, Earthsea is an early Iron Age society, with bronze used in places where iron is scarce. Ged's father is a bronze-smith. Weapons also include the use of wood and other hard but easily crafted metals. The overall climate of Earthsea is temperate, comparable to the mid-latitudes of the northern hemisphere. There is a yearly transition from warm summers to cold and snowy winters, especially in northern islands like Gont and Osskil. In the southern regions of Earthsea it can be much warmer.

The racial characteristics of the people of Earthsea are for the most part "red-brown" in coloring; in the South and East Reach and on Way, they are much darker brown, and with straight black hair; in Osskil, they have light skin, presumably with skin that is lighter in comparison to lands to the south of Osskil such as Gont or Havnor, and the Kargs of the northeastern islands, seen by the Hardic peoples as barbarians, have blonde hair and white skin.

Le Guin has criticized what she describes as the general assumption in fantasy that characters should be white and that the society should resemble the Middle Ages.

The people of the Archipelago are united by a single language: Hardic. Though dialects have inevitably sprung up on the various islands, all are mutually intelligible. The Kargs speak Kargish, and on the island of Osskil, the inhabitants also speak Osskili.

Dragons talk in True Speech, also called Old Speech, the original language of magic.

Earthsea, with the exception of the Kargad lands, is a literate society using a writing system called the "Hardic runes". The name suggests similarity to the Germanic runes, but there are supposed to be hundreds of runes in use (in A Wizard of Earthsea, Ged learns to read and write "The Six Hundred Runes of Hardic"), suggesting a logographic system similar to Chinese.

Each individual among the Hardic people has several names over the course of their life: a child-name, a use-name and a true name. Up to puberty, a person is known by their child-name; at their rite of Passage, at about the age of thirteen, that name is taken from them and they are given their true name by a witch, sorcerer or wizard. The true name is a single word of True Speech. One's true name is a closely guarded secret, shared only with those whom they trust completely because it grants the knower great power over the person. A use-name is adopted for everyday dealings. It may be an animal (Dragonfly, Hare, Otter, Sparrowhawk), a plant (Alder, Heather, Moss, Rowan), a substance (Diamond, Flint, Ivory, Jasper, Onyx) or something else (Golden, Kurremkarmerruk, the latter having no meaning). Use-names are not unique; there are, for instance, three different characters called Rose.