Ostoher is a fictional character in J. R. R. Tolkien's universe of Middle-earth.

He was the son and successor of King Anardil of Gondor and he became the seventh King upon Anardil's death in 411 T.A.

He made Minas Anor his summer residence and under his reign the Easterlings started attacks on Gondor.

He sent his son Tarostar to meet the Easterling threat and Tarostar forced the Easterling into submission.

Ostoher died in 492 T.A. and was succeeded by Tarostar.