A solitary, strong-swimming apex predator, the great hammerhead feeds on a wide variety of prey ranging from crustaceans and cephalopods, to bony fish, to smaller sharks.

[6] As a result, great hammerhead populations are declining substantially worldwide, and it has been assessed as critically endangered by the International Union for Conservation of Nature (IUCN) as of 2019.

[7] For many years, though, the valid scientific name for the great hammerhead was thought to be Sphyrna tudes, which was coined in 1822 by Achille Valenciennes.

They favor coral reefs, but also inhabit continental shelves, island terraces, lagoons, and deep water near land.

[7][8] The heaviest known great hammerhead is a female, 4.4 m (14 ft) long and 580 kg (1,280 lb) in weight caught off Boca Grande, Florida, in 2006.

[15] The great hammerhead is parasitized by several species of copepods, including Alebion carchariae, A. elegans, Nesippus orientalis, N. crypturus, Eudactylina pollex, Kroyeria gemursa, and Nemesis atlantica.

[7] The great hammerhead shark is an active predator with a varied diet, known prey of the great hammerhead include invertebrates such as crabs, lobsters, squid, and octopus; bony fishes such as tarpon, sardines, sea catfishes, toadfish, porgies, grunts, jacks, croakers, groupers, flatfishes, boxfishes, and porcupine fishes; and smaller sharks such as smoothhounds.

[8] At Rangiroa Atoll, great hammerheads prey opportunistically on grey reef sharks (Carcharhinus amblyrhynchos) that have exhausted themselves pursuing mates.

Great hammerheads primarily hunt at dawn or dusk, swinging their heads in broad angles over the sea floor so as to pick up the electrical signatures of stingrays buried in the sand, via numerous electroreceptory organs located on the underside of the cephalofoil.

[8] Another function of the cephalofoil is suggested by an observation of a great hammerhead attacking a southern stingray (Dasyatis americana) in the Bahamas; the shark first knocked the ray to the sea bottom with a powerful blow from above, and then pinned it with its head while pivoting to take a large bite from each side of the ray's pectoral fin disc.

[20] A great hammerhead has also been seen attacking a spotted eagle ray (Aetobatus narinari) in open water by taking a massive bite out of one of its pectoral fins.

The shark uses its very large dorsal fin to help achieve lift, a habit that had previously been noted in captive specimens, and may spend up to 90% of its time in this swimming orientation.

[7] Females breed once every two years, giving birth from late spring to summer in the Northern Hemisphere and from December to January in Australian waters.

[26] The great hammerhead is regularly caught both commercially and recreationally in the tropics, using longlines, fixed bottom nets, hook-and-line, and trawls.

[7] The great hammerhead is also taken unintentionally as bycatch and suffers very high mortality, over 90% for fisheries in the northwest Atlantic and the Gulf of Mexico.

[29][30] The great hammerhead is extremely vulnerable to overfishing due to its low overall abundance and long generation time.

It is also endangered in the southwestern Indian Ocean, where large numbers of longline vessels operate illegally along the coasts for hammerheads and the giant guitarfish (Rhynchobatus djiddensis).

The great hammerhead catch rate in Indian Ocean has declined 73% from 1978 to 2003, though whether these represent localized or widespread depletions is uncertain.

The great hammerhead is critically endangered along the western coast of Africa, where stocks have collapsed, with an estimated 80% decline in the past 25 years.

Concern has arisen there over a substantial increase in illegal, unreported, and unregulated fishing, reflecting the rising value of this shark's fins.

It is listed on Annex I, Highly Migratory Species, of the UN Convention on the Law of the Sea, though no management schemes have yet been implemented under this agreement.