Arathorn was the fifteenth Chieftain of the Dúnedain from TA 2930 to TA 2933. He lived for 60 years (if we take the birthyear set forth for him in HoMe as TA 2873 to be fact), a very short time for a Dúnedain. He was the son of Arador, and the husband of Gilraen, daughter of Dírhael. When they married, Arathorn was 56, and Gilraen was 22. Gilraen's father was at first opposed to the marriage.

The year after their marriage, Arador was slain by trolls, and Arathorn took the title of Chieftain. In the next year, Gilraen gave birth to Aragorn.

Arathorn was killed two years later when he went hunting orcs. He was shot through the eye with an arrow.