Tar-Minastir (1474 - 1873 S.A., r. 1691 - 1869 S.A.) was the 11th ruler of Númenor. He succeeded his aunt, Queen Tar-Telperiën. He was the grandson of King Tar-Súrion. His name means "Tower-watcher", which perhaps signifies "The Vigilant".
Sauron invaded Eriador from Calenardhon in 1695 and realms of Eregion fell. Sauron advanced to Lindon and Rivendell. In 1700 Tar-Minastir sent a navy under the command of Ciryatur, to save Lindon. Ciryatur's forces stopped Sauron's army at the river Gwathló; reinforcements from Lindon and Tharbad helped defeat Sauron at the Battle of Gwathló. Sauron retreated to Mordor in 1701 S.A.