The Hawaiian blackhead triplefin (Enneapterygius atriceps), also known as the Hawaiian triplefin in Hawaii, is a species of triplefin blenny in the genus Enneapterygius. It is a tropical blenny found in coral reefs in the Pacific Ocean, from the Hawaiian Islands, French Frigate Shoals, Laysan Island, and Midway Atoll. Blennies in this species swim at a depth range of 1-23 metres, and inhabit dead coral and rock. It was originally described by O.P. Jenkins in 1903, as a species of Tripterygion, but was reassigned to Enneapterygius by R. Fricke in 1997.