ABSTRACT The species of Hesione Savigny in Lamarck, 1818 are among the most colorful marine benthic annelids, but their pigmentation often fades in ethanol, rendering it of little use as a diagnostic feature. Further, the body includes only 16 chaetigers but because parapodia are modified after preservation, several authors have lumped most species under a few names. The digestive and reproductive systems are known for a single species (H. sicula delle Chiaje, 1830), and its gonads are hermaphroditic. In order to improve our knowledge of the genus, available specimens in the larger collections of the world were studied under a standardised approach, parapodial/neurochaetal features were defined following previous guidelines, and pigmentation patterns were reassessed. Some observations were made on the digestive system and on some details of the gonads, including Scanning Electron Microscopy (SEM) photos of sperm. Hesione includes 23 species. Twelve were already known: H. ceylonica Grube, 1874 reinstated; ...