A hammerhead shark has a wide head shaped like a hammer. This wide head is called the cephalofoil. The eyes are at the two ends of the head, and the wide-set eyes give the shark good sight. It also has electrical sense organs called the ampullae of Lorenzini.

The great hammerhead is the biggest kind of hammerhead shark. On an adult great one, the front edge of the head is nearly straight. A scalloped hammerhead is another kind. It has a notch in the middle of the front of its head.

As of November 2026, the longest great hammerhead reported was 610 centimeters (20 feet) long. As of November 2026, the largest published weight for a great hammerhead is 449.5 kilograms (991 pounds).

As of November 2026, the longest scalloped hammerheads reported reach 430 centimeters (14 feet). As of November 2026, the largest published weight for a scalloped hammerhead is 152.4 kilograms.

Hammerhead sharks live in warm seas around the world. A great hammerhead lives close to the shore and also far out at sea. It is found in water from 1 to 300 meters deep. It is usually found in water 1 to 100 meters deep. It is often found near reefs and the bottom, in water 1 to 80 meters deep. Scalloped hammerheads have been recorded at depths of 275 meters.

A hammerhead eats fish, squid and crustaceans such as crabs. A great hammerhead likes to eat stingrays, groupers and sea catfishes. Scalloped hammerheads feed mainly on bony fishes, along with cephalopods such as squid and other invertebrates.

As of November 2026, the IUCN Red List lists the great hammerhead as Critically Endangered. As of November 2026, it also lists the scalloped hammerhead as Critically Endangered.

Great hammerheads migrate with the seasons. Scalloped hammerheads migrate with the seasons too. Some travel in large schools heading north for the summer.

A mother hammerhead gives birth to live pups. A mother scalloped hammerhead carries her pups for 9 to 10 months before they are born. A great hammerhead pup is 50 to 70 centimeters long when it is born.

Young scalloped hammerheads swim together in large schools. Adult scalloped hammerheads form schools in which the sexes are mostly kept apart.

Words to know

• cephalofoil: wide hammer head
• ampullae: electric sense organs
• migrate: travel with seasons
• cephalopods: squid and kin
• invertebrates: animals without backbones