The Cordillera Occidental (English: Western Ranges) is the lowest in elevation of the three branches of the Colombian Andes.

[2] From this massif the range divides further to form the Serranías de Ayapel, San Jerónimo and Abibe.

[3] The western part of the mountain range belongs to the Pacific region of Colombia, with the San Juan River being the main watershed, while the eastern part belongs to the Cauca River basin.

The northern and northwestern parts belong to the Atlantic Slope, with the Atrato and Sinú Rivers being the main watersheds.

The Northwestern Andean montane forests cover the humid western slopes of the range.