Oscarella nathaliae is a species of sponge in the order Homosclerophorida, first found in vertical walls of reef caves at depths of about 23 to 28 metres (75 to 92 ft) in the Caribbean Sea. It has a leaf-like flat body, which is loosely attached to the substrate and a perforated, unlobate surface; it contains two bacterial wikt:morphotypes and is characterized by two mesohylar cell types with inclusions.