What is the largest volcano in the Solar System?

Olympus Mons is recognized as the largest volcano in the Solar System. It is located on Mars and stands roughly 13.6 miles (22 kilometers) high, which is nearly three times the height of Mount Everest, Earth's tallest mountain. Olympus Mons has a diameter of about 370 miles (600 kilometers), making it significantly larger in area than any volcano on Earth.

Additionally, Olympus Mons is characterized by its broad, gently sloping profile, which differs from the steeper cones of many terrestrial volcanoes. The structure of Olympus Mons and its overall dimensions indicate that it has not erupted in a long time, allowing it to accumulate vast amounts of lava over time, contributing to its enormous size.

The other options represent volcanoes or geological features on Earth. Mauna Kea is a large shield volcano in Hawaii, while Mount St. Helens is a stratovolcano known for its explosive eruptions. Mount Everest, while the tallest mountain, is not a volcano at all. Hence, none of these can compare to Olympus Mons in size and stature.