Cosmoselachus is an extinct genus of symmoriiform chondrichthyan from the Upper Carboniferous (Mississippian subperiod) aged Fayetteville Shale of Arkansas, United States.

The genus contains a single species, C. mehlingi, which is known from a partial specimen that includes the cranium, jaws, gill arches, pectoral fins, and teeth.

[1] The Cosmoselachus holotype specimen, AMNH FF 20509, was discovered in 1979 in sediments of the Fayetteville Shale near Cove Creek in Searcy County, Arkansas, United States.

[1][2] In 2024, Allison Bronson and others described Cosmoselachus mehlingi as a new genus and species of shark-like cartilaginous fish based on these fossil remains.

The generic name, "Cosmoselachus", combines "Cosm", the nickname of AMNH museum specialist Carl Mehling, with the Greek "σέλαχος" ("selachos"), which refers to cartilaginous fish.