The Round World Version is an alternative creation myth to the version of J.R.R. Tolkien's legendarium as it appears in The Silmarillion and The Lord of the Rings. In that version, the Earth was created flat and was changed to round as a cataclysmic event during the Second Age in order to prevent direct access by Men to Valinor, home of the immortals. In the Round World Version, the Earth is created spherical from the beginning.

The cosmology of J. R. R. Tolkien's legendarium combines aspects of Christian theology and metaphysics with pre-modern cosmological concepts in the flat Earth paradigm, along with the modern spherical Earth view of the Solar System.