Arda is the name of J.R.R. Tolkien’s fictional world.
In Tolkien’s mythology, Arda is the world created within Eä, the wider universe. It includes the lands and seas where the major events of Tolkien’s legendarium occur. Middle-earth is only one region of Arda, not the name of the entire world.
Arda changes through the great ages and cataclysms of Tolkien’s history. The destruction of Beleriand at the end of the First Age and the reshaping of the world after the downfall of Númenor are among the events that alter its geography. Aman, including Valinor, is another major region associated with Arda.
A frequent misconception treats “Middle-earth” and “Arda” as exact synonyms. Tolkien used Middle-earth for the central inhabited lands of his stories, while Arda has the broader geographical and cosmological meaning. This distinction matters when describing the setting of The Silmarillion and The Lord of the Rings.