In The Lord of the Rings, Aragorn takes the royal name Elessar as king.
After the defeat of Sauron, Aragorn is crowned King of the Reunited Kingdom, bringing together Gondor and Arnor. Elessar is an Elvish name meaning “Elfstone,” referring to the green jewel associated with him. Galadriel gives Aragorn a green stone, and the title connects his kingship with the blessing and friendship of the Elves.
Aragorn’s royal identity is also tied to his descent from Isildur and the kings of Númenor. Before becoming king, he is known by several names, including Strider among the Rangers and Thorongil during an earlier period of service. These names describe different stages of his life rather than replacing his royal title.
The name Elessar should not be confused with Telcontar, the name of Aragorn’s royal house. Tolkien’s appendices explain that Aragorn ruled under the name Elessar and founded the House of Telcontar.