Olympus Mons is located between the northwestern edge of the Tharsis region and the eastern edge of Amazonis Planitia. It stands about from the other three large Martian shield volcanoes, collectively called the Tharsis Montes (Arsia Mons, Pavonis Mons, and Ascraeus Mons). The Tharsis Montes are slightly smaller than Olympus Mons.