This is a bit of a trick question! It depends on how you define "highest" and "from top to bottom".

* Highest above sea level: Mount Everest is the tallest mountain on Earth, reaching 8,848.86 meters (29,031.7 feet) above sea level.

* Highest from base to summit: Mauna Kea, a volcano on the island of Hawaii, is the tallest mountain if measured from its base on the ocean floor to its summit. While only 4,205 meters (13,796 feet) above sea level, its base is roughly 6,000 meters (19,685 feet) below the ocean surface, making its total height around 10,210 meters (33,500 feet).

So, the answer depends on what you consider "highest" and how you define "top to bottom".