A new seguenziid gastropod, Basilissopsis hakuhoae, is described from 5473-5762 m depths of the oceanward slopes of the Japan and Kurile Trenches, western North Pacific Ocean. This new species is characterized by its large trochiform shell with a shoulder spiral, a bicarinate periphery, and secondary spiral riblets crossing with sigmoidal axial riblets allover the shell surface. Because the combination of these shell characters would be unique in Seguenziidae, the generic placement of this new species is by no means definitive.