Selenosteidae is an extinct family of small to large-sized arthrodire placoderms from the Late Devonian.

With the exception of the Chinese Phymosteus, selenosteids lived in shallow seas in what is now Eastern North America (the Cleveland Shale), Eastern Europe (Holy Cross Mountains, Poland, and the Kellwasserkalk fauna of Bad Wildungen), and Northeastern Africa (the Anti-Atlas Mountains, Morocco).

Selenosteids have, in cross section, a rounded body, a blunt snout, and tremendous orbits.

The cladogram below shows the placement of Selenosteidae within Eubrachythoraci:[3] Coccosteomorphi Rhachiosteus pterygiatus Eastmanosteus calliaspis Eastmanosteus pustulosus Kiangyousteus yohii Golshanichthys asiatica Westralichthys uwagedensis Dunkleosteus raveri Dunkleosteus terrelli Dunkleosteus amblyodoratus Heterosteus ingens Yinosteus major Tapinosteus heintzi Bullerichthys fascidens Kendrickichthys cavernosus Bruntonichthys multidens Dinichthys herzeri Hadrosteus rapax Gorgonichthys clarki Heintzichthys gouldii Pachyosteus bulla Gymnotrachelus hydei Stenosteus angustopectus Brachyosteus dietrichi Melanosteus occitanus Rhinosteus parvulus Below is a more detailed cladogram of Selenosteidae, from Rücklin (2011):[2] Parabelosteus Brachydeirus Pachyosteus Selenosteus Stenosteus Gymnotrachelus Microsteus Walterosteus Draconichthys Enseosteus Melanosteus Rhinosteus Denison (1978)[1] separated Selenosteidae into two informal groups, the "American" genera (i.e., those taxa from the Upper Famennian Cleveland Shales, such as Selenosteus and Gymnotrachelus), and the "European" genera (i.e., those taxa from the Upper Frasnian Kellwasserkalk facies of Germany, and later, Morocco, like Rhinosteus and Microsteus).

Denison notes that the differences between the two groups, such as how the American genera tend to have slightly smaller orbits, and slightly longer cheeks, may suggest the similarities between them are due to parallel evolution.