Eugen von Daday or Jenő von Daday (1855–1920) was an ethnic Romanian professor of zoology in Hungary in the late 19th and early 20th century.[1][2][3] Daday was an expert on aquatic invertebrates, particularly crustaceans.[4] Daday collected and identified many species and genera within the borders of the Hungarian empire, and received samples of invertebrates from collectors around the world.[4] After his death in 1920, Daday's collection of crustaceans was acquired by the Hungarian Natural History Museum.[4]