Sebastolobus altivelis, the longspine thornyhead, is a species of marine ray-finned fish belonging to the subfamily Sebastinae, the rockfishes, part of the family Scorpaenidae.

Sebastolobus altivelis was first formally described in 1896 by the American ichthyologist Charles Henry Gilbert with the type locality given as being south of the Alaskan Peninsula at Albatross station 3338 at a depth 625 fathoms.

The overall color is red to orange-red with white blotches on their back, cheeks, and the spiny part of the dorsal fin.

[1] Sebastolobus altivelisis native to the cold waters of the northeastern Pacific Ocean and is found from the Aleutian Islands, Alaska to southern Baja California, Mexico.

[4] Sebastolobus altivelis is a solitary species which typically lies motionless on the seabed for long periods of time.

As the juveniles mature they gradually move into deeper waters although they usually remain at depths of around 600 m (2,000 ft), in the mesopelagic zone.