The giant Pacific octopus is the largest kind of octopus in the world. As of November 2026, the Seattle Aquarium says adults weigh 40 to 100 pounds, with a relaxed tip-to-tip span of 12 to 14 feet. Another source puts a full-grown one at 50 pounds (23 kg) or more.

As of November 2026, an Alaska species guide lists male giant Pacific octopuses at up to 45 kg (100 lb) and 250 cm total length, and females at up to 23 kg (50 lb). Monterey Bay Aquarium and the Alaska Wildlife Alliance both say the heaviest on record weighed 200 pounds and measured nearly 20 feet across.

A giant Pacific octopus has three hearts and blue blood. Of its three hearts, two pump blood to the gills and one pumps blood to the rest of the body. It has eight arms, and the suckers on them help it grip things and taste them.

A giant Pacific octopus can move quickly by jet propulsion, shooting water out of its siphon. When threatened, it can release ink. It can also change the color of its skin to blend in, and it can squeeze through a very small space.

A giant Pacific octopus has sharp vision. It is mostly active at night, and it hunts at night. Its food includes crabs, clams, shrimp, scallops, snails and small fish. When it hunts fish, it may use a toxic saliva to paralyze them.

How smart is a giant Pacific octopus? Giant Pacific octopuses are smart: they can learn to open jars. They can tell individual people apart. A giant Pacific octopus has a well-developed brain.

In Alaska, giant Pacific octopuses are both predators and prey in the marine ecosystem. Few animals prey on a full-grown one. The main ones are large fish and marine mammals such as sea lions. Giant Pacific octopuses live from southern California north to Alaska and the Bering Sea, and across the Pacific to Japan.

A giant Pacific octopus lives about 3 to 5 years. A female breeds only once in her life. Giant Pacific octopuses breed near the end of their lives and die not long after. A female lays about 20,000 to 100,000 eggs in a den and stays with them, usually not eating, until they hatch.

The eggs take roughly 5 months to a year to hatch, depending on the water temperature. A baby is about the size of a grain of rice when it hatches. After hatching, the tiny octopuses drift near the ocean surface as plankton. About one percent of giant Pacific octopus larvae survive their drifting plankton stage.

Words to know

• siphon: water tube
• ecosystem: living community
• larvae: baby stage
• plankton: drifting life