Icaronycteris is an extinct genus of bat that lived in the early Eocene (approximately 52.2 million years ago). Specimens are known from the Green River Formation of North America. Type specie is Icaronycteris index.
Animal had a wingspan of 37 centimeters (15 in). Icaronycteris slept while hanging upside down, holding onto a tree branch or stone ridge with its hind legs.