Protospinax is an extinct genus of cartilaginous fish found in the Solnhofen limestones of southern Bavaria. It is a difficult taxon to accommodate in taxonomies. Formerly known from only two specimens, further museum specimens were discovered at the Museum of Comparative Zoology of Harvard University in the 1990s, having been misidentified as Squatina and Heterodontus.
Protospinax was about 1.7 m in length.