Which is the most massive volcano in the Solar System?

Olympus Mons is the largest volcano in the Solar System and is found on Mars. It stands about 22 kilometers high, making it nearly three times taller than Mount Everest above sea level. The volcano is also enormous across its base, spanning roughly 600 kilometers. Its size is possible because Mars has lower gravity and no active plate tectonics like Earth. Olympus Mons is a shield volcano, built by repeated lava flows over a very long time.