Third Earth is a fictional planet featured in the animated television series ThunderCats. It serves as the primary setting for the adventures of the ThunderCats, a group of cat-like humanoid warriors. The planet is characterized by its diverse landscapes, including forests, mountains, and deserts, and is home to various creatures and civilizations. The story begins when the ThunderCats flee their home planet, Thundera, after it is destroyed. They arrive on Third Earth, where they face challenges from villains like Mumm-Ra, the main antagonist. The series explores themes of heroism, friendship, and the struggle between good and evil.