The planet known for having the tallest volcano is Mars. Olympus Mons, located on the Martian surface, is the tallest volcano in our solar system, reaching approximately 13.6 miles (22 kilometers) high. This shield volcano is about 370 miles (600 kilometers) in diameter, making it roughly the same size as the state of Arizona. Its size and distinct flanks have made it a focal point of interest for scientists studying volcanic activity and planetary geology.