The sword forged from Narsil and carried by Aragorn in J.R.R. Tolkien’s The Lord of the Rings is Andúril.
Narsil was the sword of Elendil, who used it against Sauron at the end of the Second Age. Although Elendil was killed, his son Isildur used the broken blade to cut the One Ring from Sauron’s hand. The sword was then broken and kept as an heirloom of Isildur’s line.
In The Lord of the Rings, the shards of Narsil are reforged for Aragorn before he claims his royal heritage openly. The new sword is named Andúril, Flame of the West. Its reforging symbolizes the restoration of the line of kings and Aragorn’s readiness to lead.
Andúril is sometimes confused with other famous Tolkien swords. Glamdring belongs to Gandalf, Orcrist was associated with Thorin Oakenshield, and Sting was Bilbo’s and later Frodo’s smaller sword.