The hive ship is the massive mothership of the Wraith, the dominant race of the Pegasus Galaxy that feeds on humans by drawing the life force from them. The hive ship is enormously powerful, a match for the BC-304 class of battleships and capable of targeting a planet from orbit.
SG-1 encountered a Wraith hive ship during the mission to Atlantis. The Odyssey launched a stargate toward the accretion disk of a black hole in the Pegasus Galaxy and prepared to use warheads to force the active wormhole to arc to the supergate in the Milky Way. As they drew closer to the black hole, however, sensors and communications were affected, and they were unaware that a Wraith hive ship was approaching their position. As they came under fire, Odyssey lured the Wraith ship toward the black hole and beamed two warheads aboard the hive ship as it drew near the active stargate, then used the gravity well to slingshot themselves away from the vortex. The hive ship exploded, and the resulting energy spike not only caused a wormhole arc to the supergate in the Milky Way Galaxy, but the kawoosh of the activating supergate also destroyed an Ori warship waiting near the event horizon.
Episode Reference: The Pegasus Project