Which marine animal has the largest brain of any animal?

The sperm whale has the largest brain of any animal.

An adult sperm whale’s brain can weigh about 7 to 9 kilograms, making it the heaviest brain known in the animal kingdom. Brain size alone does not measure intelligence, but sperm whales have complex social lives, sophisticated communication and specialized adaptations for deep-water hunting.

Sperm whales are famous for feeding on squid, including giant squid, at great depths. They can make prolonged dives and use echolocation clicks to locate prey in darkness. Their enormous forehead contains the spermaceti organ, a structure involved in sound production and focusing echolocation signals.

The species is also the largest toothed whale. Historical whaling targeted sperm whales for oil from the spermaceti organ and other products, causing major population declines. International protections have reduced direct hunting, although modern threats include entanglement, ship strikes and ocean noise.