Gyūki

The Eight-Tailed Beast is currently one of the two remaining Tailed Beasts that was not extracted by Akatsuki, while the other one being the Nine-Tailed Demon Fox. Due to Akatsuki's depleted numbers, Madara Uchiha ordered Team Hawk to capture the Eight-Tailed Beast. In return, Madara Uchiha will allow Team Hawk to use a Tailed Beast to destroy Konohagakure.
 * Name:
 * Creature Type: Unknown
 * Host: Unknown
 * Unique Traits: Unknown
 * Status: Active

Speculation
As most of the other Tailed Beasts are based upon mythological creatures, it is speculated that the Eight-Tailed Beast is based upon the eight-headed and eight-tailed dragon, Yamata No Orochi.