Titan

Titan is a moon of the planet Saturn. It is also the planet's largest moon and has a very dense atmosphere.

The Transformers cartoon
Titan was home to a race of blue-skinned humanoids whose society was dominated by a caste of corrupt astrologer priests (led by Jero) that used a false "sky god" (actually a statue with movable arms) to frighten the masses into submission. Astrotrain arrived on Titan and declared himself a god, with the intention of forcing the Titanians to mine energy crystals on the Decepticons' behalf. Several Autobots showed up and defeated Astrotrain and the astrologer priests who had aligned themselves with him, leaving the rebel leader Talaria to begin building a more enlightened society.

Later, the moon was terraformed (no mention of what happened to the natives). It then became home to a secret Quintesson base. Three of the Technobots flew to investigate, but were shot down by Abominus and crashed on its surface. Their comrades eventually rescued them; repaired, the team defeated the Terrorcons and compelled the Quints to flee.

Zone
Metrotitan was built on Titan.