The sword reforged for Aragorn in J.R.R. Tolkien’s The Lord of the Rings is Andúril.
Andúril means “Flame of the West” in Quenya. It was made by reforging the shards of Narsil, the sword used by Elendil against Sauron at the end of the Second Age. Isildur cut the One Ring from Sauron’s hand with the broken blade, after Elendil was killed.
The reforging symbolically connects Aragorn with the kings of Númenor and Gondor. In the novel, the sword is remade before Aragorn’s journey south with the Fellowship. Its presence supports his claim to the throne and recalls the history that makes him the heir of Isildur.
Andúril is often confused with other famous Tolkien swords. Glamdring belongs to Gandalf, Sting belongs to Bilbo and Frodo, and Orcrist was carried by Thorin Oakenshield.