Firestar is a bright flame-colored tabby tom with emerald-green eyes.

Firestar was a leader of Thunderclan in the forest and the lake territories. He was born to Jake and Nutmeg, and lived as a kittypet named Rusty. He joined ThunderClan as an apprentice, receiving the name of Firepaw, and was mentored by Lionheart and Tigerclaw before being assigned to Bluestar. Fireheart earned his warrior name, and ascended to deputyship after Tigerclaw's banishment. He also mentored Cinderpelt before her injury, his nephew, Cloudtail, and Tigerclaw's son, Brambleclaw. After Bluestar's death, he rose to leader as Firestar appointing Whitestorm as his second-in-command. He later passed the role to Graystripe upon the white deputy's death during the battle against Bloodclan, and defeated Scourge. Firestar became mates with Sandstorm, and they went on a journey to rebuild Skyclan. They were successful, and upon their return, had two daughters together: Leafpool and Squirelflight.