Widespread in temperate and tropical seas. Western Atlantic: Canada to the Virgin Islands; Brazil to Argentina. Eastern Atlantic: British Isles to Côte d'Ivoire, including the Mediterranean. Indo-Pacific: South Africa to Sri Lanka; southern Siberia to Viet Nam; southern Australia, New Zealand, and Hawaii. Eastern Pacific: northern California, USA to Chile.

A large hammerhead with a notch at the center of head; 1st dorsal fin moderately high, 2nd dorsal and pelvic fins low. Olive-grey or dark grey above, white below. Fins nearly plain, dusky or blackish tipped.

Occurs inshore and well offshore, over continental and insular shelves. Coastal, pelagic, and semi-oceanic, but often bottom associated at 1-139 m. Migrates northward in summer; young often in large aggregations of hundreds of individuals. Prefers to feed on small sharks, skates and stingrays, but also preys on bony fishes, shrimps, crabs, barnacles and cephalopods. Viviparous. Regarded as being dangerous to people, though only few can be tentatively attributed to this species due to its occurrence in temperate waters.