Andúril was the most famous sword in J.R.R. Tolkien's The Lord of the Ring trilogy. Its name literally means "flame of the west." It is also referred to as "the sword of Elendil," who was its first owner.
The sword was originally called "Narsil," and was referred to as "the sword that was broken." It became called "Andúril" after some friendly elves forged the broken blade for Aragorn, son of Arathorn.
Aragorn was a direct descendant of Isildur, the very same person after whom the phrase "Isildur's Bane" was named. When Isildur finally stole the One Ring from the Dark Lord, Sauron, the ring betrayed him. As he was crossing a river under the cloak of the One Ring, the ring made him visible again and he was shot with many poisoned arrows from a band of Orcs. It was for this reason that through the concept of male-lineage which is common throughout mythology, that it was Aragorn's duty to save Middle Earth and to assume his rightful position as king of Gondor.