Thallassa is a planet in the Unknown Regions of space.

A water planet rich in sea life and sparse in land mass. Many species thrive around the tropical equator. Most species assume an amphibious existence living a double life in the sea and on the small patches of land. The prominent sentient species, know as Thallassans, developed in the water but eventually grew accustomed to living on land. The other sentient species on the planet were known as the Delphi, who were solely aquatic.

The two continents of Thallassa reside just above the equator and at the south pole. About 10% of the planet is land.

During the Clone Wars, Thallassa was destroyed by the Droid Army controlled by the Separatists. The oceans were boiled away and much of the life on the planet was destroyed. It is currently unknown if the planet is still habitable.