A new treehopper genus Selenacentrus (Membracidae: Centrotinae), and new species, S. wallacei, from the southwestern United States and northern Mexico, are described and illustrated. This genus lacks key characteristics of currently recognized New World centrotine tribes including the dorsoapical and ventral lobes of the male lateral plate and cucullate setae of the mesothoracic femora (characteristic of the Boocerini). It also lacks the additional m-cu crossvein and broadened second valvulae characteristic of Platycentrini. The narrow, curved second valvulae, with prominent dorsal teeth, and lateral exposure of the scutellar apices resemble those of some endemic Antillean centrotines (Monobelini, Nessorhinini); however, Selenacentrus differs from these groups in characters of the forewing and male genitalia.