Eärnur was the son of Eärnil II and became upon his death in 2043 T.A. the thirty-third and last King of Gondor, before the Stewards of Gondor took it upon themselves to rule the realm.

He was a great general and his greatest victory was in 1975 T.A. in the Battle of Fornost against Angmar which he destroyed.

After becoming King he was challenged two times by the Witch-King of Angmar, chief of the Ringwraiths, who now resided in Minas Morgul. The first challenge went unanswered but in 2050 T.A the second one came and he accepted. After entering the gates of Minas Morgul he was never heard from again.

No new king was elected and the rule of Gondor passed to the Stewards. They were to rule "until the King returns" for it wasn't sure whether Eärnur was killed or not.