Aragorn took the title King Elessar when he became king in J.R.R. Tolkien’s The Lord of the Rings.
After Sauron’s defeat, Aragorn is crowned King of the Reunited Kingdom, joining Gondor and Arnor under one ruler. Elessar is a Quenya name meaning “Elfstone,” linking the king with the green jewel associated with his healing and royal identity.
Aragorn also bears the royal name Telcontar, meaning “Strider” in Quenya. The name reflects his earlier identity as a ranger traveling under the nickname Strider, before his lineage and claim to the throne are openly accepted.
King Théoden is the ruler of Rohan, while Isildur was Aragorn’s ancestor and an earlier king. These names belong to the same broad history but are not Aragorn’s coronation title.