What's the biggest volcano in the Solar System?

This image provides a perspective view of Olympus Mons. North is to the left of the image. Perspective combining Viking imagery and topography data, available Online from: http://stardust.jpl.nasa.gov/planets/gif/mar/olympers.gif

So far, the largest volcano in our Solar System is Olympus Mons on Mars. It is about 17 miles (27 km) tall. That's a long hike for some future explorer. Mount Everest is about 6 miles (10 km) tall.

Steve Mattox and Robert Wickman

Volcanism on Mars