The planet that has the largest volcano in the solar system is Mars. This volcano, named Olympus Mons, stands approximately 13.6 miles (22 kilometers) high, making it nearly three times the height of Mount Everest. Olympus Mons is a shield volcano, characterized by its broad, gently sloping sides formed by the eruption of low-viscosity lava. The volcano's size is attributed to the lower gravity on Mars and the planet's lack of tectonic plate movement, allowing lava to accumulate over an extended period. Olympus Mons is a notable feature in planetary geology, illustrating the volcanic activity of Mars.