The White Ship was the ship that sailed from the Grey Havens to the Undying Lands, carrying the Ring-bearers after the War of the Ring. Its departure marked the end of the Third Age.

On the White Ship were Elrond, Galadriel, and Gandalf, who had been the Keepers of the Three Elven Rings. With them went the Hobbits who had borne the One Ring, Bilbo and Frodo. Also apparently onboard the ship was Gandalf's faithful companion, Shadowfax.

Other Elves journeyed to the Grey Havens with those who we know boarded the ship, but whether or not they too embarked on that same craft is unknown.
Encyclopedia entry originally written by astro1014