Stromerius is an extinct genus of basilosaurid early whale known from the Late Eocene (Priabonian, 37.2 to 33.9 million years ago) of Fayum, Egypt (29°36′N 30°36′E / 29.6°N 30.6°E, paleocoordinates 24°54′N 26°30′E / 24.9°N 26.5°E). made S. nidensis the type species of the subfamily "Stromeriinae", but only mentioned this proposed subfamily briefly in his abstract. They are two specimens: described and illustrated BSPM 1902.XI.504-510, seven vertebrae, and described UM 100140, 19 complete or partial vertebrae.