The Southwestern Naturalist includes scientific manuscripts that deal with living or fossil organisms, assemblages, or ecosystems that occur in Mexico, Central America, and the region of the United States west of the Mississippi River and south of 40°N latitude. Acceptable topics include anatomy, physiology, genetics, behavior, natural history, dispersal, distribution, evolution, and systematics, but this list is not comprehensive. Both feature articles and notes are published.

The Southwestern Association of Naturalists was founded in May 1953 to promote the field study of plants and animals (living and fossil) in the southwestern United States, Mexico, and Central America and to aid in the scientific activities of its members. The Association holds an annual meeting and publishes The Southwestern Naturalist. Membership is open to all persons interested in natural history.