Aldarion was the first child and only son to be born to his father Tar-Meneldur and his mother Almarian. He became the sixth of the Kings of Númenor.

Aldarion's proper name was Anardil, but he was long called by his name of Aldarion because he was greatly concerned with trees. He planted great woods to supply his ship-building efforts. He was a great mariner and ship-builder and he sailed often to Middle-earth where he became a friend and counselor of Gil-galad.

Because Aldarion was often gone for many months at a time his wife Erendis became angry and the couple separated in SA 882. She had borne to him a daughter though of great beauty named Ancalimë.

Because he had no sons, Aldarion caused the Númenórean laws of succession to be changed so that if the king had no son, his eldest daughter could then take the Sceptre. This changed displeased many of the descendants of Elros, especially Aldarion's nephew Soronto who would have taken the Sceptre under the old laws.

Tar-Aldarion reigned for 192 years and was succeeded by his daughter Tar-Ancalimë in SA 1075.