The Madrean alligator lizard (Elgaria kingii), also known commonly as King's alligator lizard and el lagarto de montaña in Mexican Spanish, is a species of lizard in the family Anguidae. The species is native to the southwestern United States and adjacent northwestern Mexico.

The specific name, kingii, is in honor of Phillip Parker King, an Australian-born Royal Navy officer who surveyed the coast of South America.

E. kingii is found from southeastern Arizona and southwestern New Mexico, United States, southward to Jalisco, Colima, Nayarit, southeastern Zacatecas, and southwestern Aguascalientes, Mexico.

E. kingii is found in a variety of habitats including desert, grassland, shrubland, and forest.

E. kingii is oviparous.

Three subspecies are recognized as being valid, including the nominotypical subspecies.

Nota bene: A trinomial authority in parentheses indicates that the subspecies was originally described in a genus other than Elgaria.