Pepemkay maya, gen. et sp. nov., is described based on a single complete specimen collected in El Chango Quarry, a marine Cenomanian limestone outcrop of the Sierra Madre Formation, near Tuxtla Gutiérrez, Chiapas State, southern Mexico. This species is identified as a new member of the Lissoberycinae and differs from other genera of this subfamily because it has an unornamented skull; bones of opercular series with non-spiny posterior borders; dorsal fin with five spines and eight soft rays; pelvic fin including a spine plus three branched soft rays; predorsal formula 0 0/0/1 1/; cycloid scales in the caudal peduncle and anterior half of the body, crenate scales between these body regions; and at least one scale on the opercle and other over the quadrate. Pepemkay maya is the first Trachichthyidae and Lissoberycinae fish found in marine Cretaceous deposits of America; its discovery complements our comprehension on the taxonomical diversity of fossil Trachichthyidae and supports the efforts directed to describe the processes involved in the evolution, origin, and early diversification of this group within an appropriate biogeographical framework, which now involves fossil evidence that has begun to appear in the Cretaceous fossil deposits of America.