The Defersi Desert is a desert on the Xersian continent. It is the largest hot desert in the world and the second largest desert overall, smaller only than the desert of Dracodryn.
The name "Defersi" comes from the name of the indigenous people of the land, the Defersi.
The desert comprises much of central Xersia, excluding the fertile regions on the coasts, the Helle Mountains, and the Cogi Valley. It stretches from the Siauras Sea in the east to the Asuanian Ocean in the west, where the landscape gradually changes from desert to coastal plains. It is bounded by the Helle Mountains to the north and the Sycla to the south. For several hundred thousand years, the Defersi has alternated between desert and savanna grassland in a 20,000 year cycle caused by the precession of Mezia's axis as it rotates around Vix, which changes the location of the central Xersian monsoon.