Naglfar, in Norse mythology, the grisly ship, made of the nails of dead men, that would carry the evil frost giants to their final battle against the gods at the time of Ragnarok, the conflict that would take place at the end of the world. At Ragnarok, the giants, eternal enemies of the gods, would attack the heavenly realm of Asgard, and the world--including gods and humans--would be destroyed.
The Norse believed that when Ragnarok approached, wolves would swallow the sun and moon, and the stars would disappear from the sky. The earth and mountains would shake so much that all the giants and monsters that had been bound by the gods would break free. Jormungand, the monstrous serpent who dwelled at the bottom of the oceans, would rise up in a rage onto the land, and this cataclysm would cause the ship Naglfar to be loosed from its moorings. It would be carried along on the tempestuous waters toward Asgard, captained by a giant named Hrym.
The word Naglfar means "conveyance made of nails." Since this ship of doom was to be made of the nails of human corpses, it was customary among ancient Norse peoples to trim short the nails of their dead; in this way, they believed, they could help to forestall the end of the world--by however small the amount--through not giving the enemy their building material.
Naglfar was also the name given to an ancient giant, the first husband of Nott (Night).