The Rebel Basestar is a Cylon Basestar inhabited by the Two, Six, and Eight models with eventually the addition of the last Three model. After the division of the models, Cavil ordered the Basestars under his command and inhabited by Ones, Fours, and Fives to attack the "Rebel Cylon Fleet" under the control of Twos, Sixes, and Eights. All of the Basestars under the command of the Twos, Sixes, and Eights were destroyed with the exception of the Rebel Basestar, though it was initially severely damaged. The damage caused by the attack in part inspired the Rebel Cylons to be amiable to forging an alliance with the Colonials.
The Rebel Basestar joined with the Colonial Fleet and was a crucial element in the eventual fate of the Humans. At the conclusion of the series, the remaining Cylons (save the last Three who chose to remain on the destroyed "Earth" that had been inhabited by humanoid Cylons and been destroyed by nuclear holocaust two thousand years prior) decided to join the Humans and take up residence on Earth. The Rebel Basestar was given to the Centurions as a gratuity for their assistance and sacrifice in the final battle between the Rebel Cylons and Cavil's forces. Its eventual fate is unknown as it leaves Earth orbit with its FTL drive.