Amastris or Amestris may refer to:

People Amastris (Amazon) Amastris (daughter of Oxyathres), Persian princess, wife of Dionysius of Heraclea Amestris, Persian queen, wife of Xerxes I, mother of Artaxerxes I Amastris, daughter of Artaxerxes II Amastris, daughter of Darius II, wife of Terituchmes

Places Amastris (city), now Amasra, in ancient Paphlagonia Amestris (Fullmetal Alchemist), a fictional country in the anime and manga series Fullmetal Alchemist

Other Amastris (treehopper), the type genus of the treehopper tribe Amastrini