Southern Athabaskan (also Apachean) is a subfamily of Athabaskan languages spoken primarily in the Southwestern United States (including Arizona, New Mexico, Colorado, and Utah) with two outliers in Oklahoma and Texas. The languages are spoken in the northern Mexican states of Sonora, Chihuahua, Coahuila and to a much lesser degree in Durango and Nuevo León. Those languages are spoken by various groups of Apache and Navajo peoples. Elsewhere, Athabaskan is spoken by many indigenous groups of peoples in Alaska, Canada, Oregon and northern California.

Self-designations for Western Apache and Navajo are N'dee biyat'i, and Diné bizaad or Naabeehó bizaad, respectively.

There are several well-known historical people whose first language was Southern Athabaskan. Geronimo (Goyaałé) who spoke Chiricahua was a famous raider and war leader. Manuelito spoke Navajo and is famous for his leadership during and after the Long Walk of the Navajo.

The seven Southern Athabaskan languages can be divided into two groups according to the classification of Harry Hoijer: (I) Plains and (II) Southwestern. Plains Apache is the only member of the Plains Apache group. The Southwestern group can be further divided into two subgroups (A) Western and (B) Eastern. The Western subgroup consists of Western Apache, Navajo, Mescalero, and Chiricahua. The Eastern subgroup consists of Jicarilla and Lipan.

Hoijer's classification is based primarily on the differences of the pronunciation of the initial consonant of noun and verb stems. His earlier 1938 classification had only two branches with Plains Apache grouped together with the other Eastern languages (i.e. with Jicarilla and Lipan).

Mescalero and Chiricahua are considered different languages even though they are mutually intelligible. Western Apache (especially the Dilzhe'e variety) and Navajo are closer to each other than either is to Mescalero/Chiricahua. Lipan Apache and Plains Apache are nearly extinct, and Chiricahua is severely endangered. Mescalero, Jicarilla, and Western Apache are considered endangered as well, with some children still learning the languages despite the number of child speakers continuing to diminish. Navajo is one of the most vigorous North American languages, but has still faced decline, with use among first-graders decreasing from 90% in 1968 to 30% in 1998.

The Southern Athabaskan languages spoken in Mexico are regulated by the Instituto Nacional de Lenguas Indígenas (INALI) and have the official status of national languages of Mexico. To revitalize the languages, the institute created a community based Language Planning Council with native speakers to establish and develop grammar rules and the normalization of the writing system, an official alphabet has been validated since then while other grammar topics are still in development.

All Southern Athabaskan languages are somewhat similar in their phonology. The following description will concentrate on Western Apache. One can expect minor variations for other related languages (such as Navajo, Jicarilla, Chiricahua).