What living animal has the heaviest brain?

The living animal with the heaviest brain is the sperm whale. Its brain weighs about 7–9 kilograms (15–20 pounds), making it several times heavier than a human brain.

The sperm whale’s scientific name is Physeter macrocephalus. Its enormous, square-shaped head can account for roughly one-third of its body length, housing a brain adapted to life in the deep ocean. Sperm whales use powerful clicks for echolocation and communication while hunting squid at depths of more than 1,000 metres.

A common mix-up is the blue whale. Blue whales are much larger overall, but their brains weigh less than a sperm whale’s. Elephants have the heaviest brains among land animals, at roughly 4–5 kilograms, while gorilla brains are far lighter. Brain weight also differs from intelligence: the sperm whale has the largest known animal brain by mass, but its brain-to-body ratio is relatively small because the whale itself is enormous.

The sperm whale’s brain is also notable for its large cerebral hemispheres and a highly developed auditory system, reflecting its dependence on sound in the dark ocean depths.