Middle-earth is the fictional setting of much of British writer J. R. R. Tolkien's legendarium. The term is equivalent to the term Midgard of Norse mythology, describing the human-inhabited world, i.e. the central continent of the Earth in Tolkien's imagined mythological past. Tolkien's most widely read works, The Hobbit and The Lord of the Rings, take place entirely in Middle-earth, and Middle-earth has also become a short-hand to refer to the legendarium or its fictional universe.
Within his stories, Tolkien translated the name "Middle-earth" as Endor (or sometimes Endórë) and Ennor in the Elvish languages Quenya and Sindarin respectively, sometimes referring only to the continent that the stories take place on, with another southern continent called the Dark Land.
Middle-earth is the north continent of Earth (Arda) in an imaginary period of the Earth's past (Tolkien placed the end of the Third Age at about 6,000 years before his own time), in the sense of a "secondary or sub-creational reality". Its general position is reminiscent of Europe, with the environs of the Shire intended to be reminiscent of England (more specifically, the West Midlands, with Hobbiton set at the same latitude as Oxford).