The High King of both Arnor and Gondor (although his 2 sons, Isildur and Anarion actually ran Gondor), he was born in Numenore as a relation of the royal family. Upon the destruction of Numenor by the Valar, he led the remnant of the Faithful Dunedain to Middle-Earth; where he and Gil-Galad re-affirmed the friendship between Men and Elves. When Sauron rose again and his forces took Minas Ithil, Elendil decided upon a do-or-die assault upon Sauron. So he went to his friend Gil-Galad, and he agreed to honor the Elves debt to Numenore; and help overthrow the Dark Lord. Thus was formed the Last Alliance. During the battle of the Last Alliance, when victory was assured and Sauron took to the battlefield, he picked up Gil-Galad by the neck; and so hot was the fire of his rage that before their eyes he burst into flames. Elendil charged Sauron in order to avenge his friend but Sauron smashed him with his mace and he was mortally wounded and died there also.
Elendil was the previous owner of Aragorn's sword, Anduril. Before it was broken its name was Narsil.