Ernst Thälmann Island (German: Ernst-Thälmann-Insel, Spanish: Cayo Ernesto Thaelmann or Cayo Blanco del Sur) is a 15 kilometre long and 500 metre wide Cuban island in the Gulf of Cazones named for German Communist politician and activist Ernst Thälmann. It contains highly developed reef formations with a high degree of biodiversity and hosts a number of endangered species, including black coral and various ornamental reef fish species. It has extensive largely untouched beaches and provides nursery areas for snappers.