Isildur is a fictional character in J. R. R. Tolkien's legendarium. He appears in the author's books The Lord of the Rings, The Silmarillion, and Unfinished Tales.
In The Lord of the Rings, he was first mentioned in The Fellowship of the Ring as a Dúnadan of Númenor, elder son of Elendil. His full character history was detailed in The Silmarillion and Unfinished Tales. He was the second king of Gondor (jointly with his brother Anárion until the latter's death) and the second king Arnor. His name means "devoted to the moon". In a note written well after the initial publication of The Lord of the Rings, Tolkien gave Isildur's height as seven feet tall.
Read more about Isildur: Development, In The Lord of The Rings, Portrayals in Adaptations, House of Elendil