Berryteuthis magister, also known as the magister armhook squid, commander squid or schoolmaster gonate squid, is a medium-sized squid in the family Gonatidae. It is found in cold, high latitude waters of the North Pacific where it is among the most numerous squid species recorded. There are three recognised subspecies of B. magister. The type locality of all three is Japan, although specimens have been recorded as far east as the Aleutian Islands.