If we use “world” to mean the universe and not just the earth, then the largest volcano that we know about is on the planet Mars.
This huge mountain, called Olympus Mons, is about 370 miles across, and its peak stands 18 miles above the surrounding land. Mount Everest, Earth’s tallest mountain, is less than 51/2 miles high.
And another Martian volcano, called Alba Patera, is about 5 miles high and almost 1,000 miles across!
