Senegalia greggii is a species of Senegalia native to the southwestern United States and northern Mexico, from the extreme south of Utah (where, at 37°10' N it is the northernmost naturally occurring Senegalia species anywhere in the world) south through southern Nevada, southeast California, Arizona, New Mexico and western Texas to Baja California, Sinaloa and Nuevo León in Mexico. The specific epithet greggii refers to Josiah Gregg, author, explorer, and amateur naturalist of the American Southwest and northern Mexico.