Mars has the largest volcano in called Olympus Mons.  Olympus Mons is the largest volcano in our Solar System.  It is three times higher than Mr. Everest!  It is as wide as the state of Arizona.  It is 50 times bigger than the Mauna Loa, Earth's largest volcano.  The top of Olympus Mons is 70 km wide.  Olympus Mons is 16 miles high and 325 miles wide.