Rhinogobiops nicholsii, commonly known as the blackeye goby, is a species of true goby in the family Gobiidae. The blackeye goby is a very common inhabitant of coral reefs and rocky habitats along the eastern Pacific coasts of Mexico, the United States, and Canada.
Forms permanent harem groups composed of a single male and several smaller females. Coloration can vary as blackeye gobies are capable of rapidly changing color during social interactions and for camouflage. The basic body color is creamy white to pale tan but can become a mottled dark purple-brown.
Blackeye gobies are protogynous hermaphrodites – all of them are born females but can shift once to become males once they reach a length of 5.1 to 7.6 cm.