Aegirocassis is an extinct genus of anomalocarid arthropod belonging to the family Hurdiidae that lived 480 million years ago during the early Ordovician. It is known by a single species, Aegirocassis benmoulai. Van Roy initiated scientific study of the fossil,the earliest known of a "giant" filter-feeder discovered to date. Aegirocassis is considered to have evolved from early predatory anomalocarids.