Though mountains are mentioned almost everywhere in Humboldt's narratives, none of his writings was specifically dedicated to mountains as a type of landform, milieu, or category of knowledge. Aiming to contribute to a greater understanding of Humboldt's worldview, this essay strives to explain why mountains are valuable as objects his reflection. It points to the frequency with which Humboldt mentions mountains in his writings, the various scientific perspectives evoked in these references, and the overall coherence of his observations and perspectives.