Sigma Supreme

First Cybertronian ship in history that hasn't violently crashed upon reentry into Earth's atmosphere.

This was the ship that the Cybertron Elite Guard had used to traveled to Earth and find Optimus Prime and his salvage crew. Most likely (without a doubt) Ultra Magnus was the captain of the ship. It has an impressive suite of defenses to keep icky organics out.

From Teletraan I: The Transformers Wiki, a Wikia wiki.