The highest mountain on Earth measured from the planet’s center is Chimborazo.
Chimborazo’s summit is about 6,384.4 kilometers from Earth’s center, farther than Mount Everest’s summit despite Everest being much higher above sea level. Chimborazo reaches roughly 6,263 meters above sea level, compared with Everest’s approximately 8,849 meters, so the answer depends entirely on the measurement used.
The explanation is Earth’s equatorial bulge. Our planet is an oblate spheroid rather than a perfect sphere: rotation makes it wider around the Equator and slightly flattened at the poles. Chimborazo lies only about one degree south of the Equator, so its summit starts from a greater distance from Earth’s center. Its equatorial position more than offsets Everest’s extra elevation.
Chimborazo is an inactive Ecuadorian stratovolcano in the Andes, with a last known eruption around AD 550. Edward Whymper made the first recorded successful ascent in 1880. The common mistake is calling it Earth’s highest mountain without specifying the measurement; Everest remains highest above sea level.