A mountainside is the sloping surface of a mountain between its base and its peak. When you look at a mountain from a distance, you're seeing its mountainside: the steep, often rocky face that rises up from the valley floor.

Mountainsides can be covered with dense forests, bare rock, meadows of wildflowers, or permanent snow and ice, depending on the climate and elevation. Hikers climbing a mountain spend most of their time traversing the mountainside, working their way up switchback trails that zigzag across the slope. In winter, skiers race down mountainsides, while in summer, mountain goats somehow manage to bound across near-vertical mountainsides with astonishing ease.

The character of a mountainside matters enormously. A gentle, grassy mountainside might host grazing sheep and scattered farmhouses. A steep, rocky mountainside requires technical climbing skills and specialized equipment. Mountain villages are often built on mountainsides, with houses terraced into the slope. When heavy rains come, unstable mountainsides can trigger dangerous landslides that send rock and soil cascading into the valleys below.