Stomiiformes is an order of deep-sea ray-finned fishes of very diverse morphology. It includes, for example, dragonfishes, lightfishes (Gonostomatidae and Phosichthyidae), loosejaws, marine hatchetfishes and viperfishes. The order contains 4 families (5 according to some authors) with more than 50 genera and at least 410 species. As usual for deep-sea fishes, there are few common names for species of the order, but the Stomiiformes as a whole are often called dragonfishes and allies or simply stomiiforms.

The scientific name means "Stomias-shaped", from Stomias (the type genus) + the standard fish order suffix "-formes". It ultimately derives from Ancient Greek stóma (στόμᾶ, "mouth") + Latin forma ("external form"), the former in reference to the huge mouth opening of these fishes.

The earliest stomiiform is Paravinciguerria from the Cenomanian of Morocco and Italy.

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