A cordillera is an extensive chain and/or network system of mountain ranges, such as those in the west coast of the Americas. The term is borrowed from Spanish, where the word comes from cordilla, a diminutive of cuerda ('rope').

The term is most commonly used in physical geography and is particularly applied to the various large mountain systems of the American Cordillera, such as the Andes of South America, and less frequently to other mountain ranges in the "ridge" that rims the Pacific Ocean. In Colombia and Venezuela, cordilleras are named according to their position: Cordillera Occidental, Central, and Oriental. Various local names are used for the cordilleras in Ecuador, Peru, Bolivia, Chile and Argentina.

Such mountain systems have a complex structure, which is usually the result of folding and faulting accompanied by volcanic activity. In South America, the ranges include numerous volcanic peaks. The Andes cordillera has Ojos del Salado, the highest active volcano in the world and second-highest point in the Western Hemisphere (though not itself a volcano, Argentina's Aconcagua, at 6,960 m or 22,830 ft, is the highest point in the Western Hemisphere). Some of the volcanoes have been active in historical times.

Aside from the volcanic peaks, the cordilleran crests include many narrow ridges, some of which reach into the zone of permanent snow. Between the ranges are numerous inhabited valleys, basins and low plateaus, with a wide range of elevations.