What name did J.R.R. Tolkien give to the main landmass of his legendarium?

J.R.R. Tolkien called the main landmass of his legendarium Middle-earth.

Middle-earth is the setting for The Hobbit and The Lord of the Rings, as well as much of The Silmarillion. It is not the entire world: in Tolkien’s cosmology, it is a region of Arda, the world created within his mythology.

The name comes from the Old English term middangeard, a word referring to the inhabited world between heaven and the underworld. Tolkien used the term in a historical and mythological sense rather than inventing it as a simple synonym for an underground place.

Other major regions belong to the same wider world. Aman lies to the west across the sea, Númenor was an island kingdom later destroyed, and Beleriand was an important western region during the First Age before it was submerged.