North Pacific Giant Octopus – Monterey Bay Aquarium, Monterey, California

Enteroctopus dofleini, also known as the giant Pacific octopus or North Pacific giant octopus, is a large marine cephalopod belonging to the phylum Mollusca, and genus Enteroctopus. Its spatial distribution includes the coastal North Pacific, along California, Oregon, Washington, British Columbia, Alaska, Russia, northern Japan and Korea. It can be found from the intertidal zone down to depths of 2,000 m (6,600 ft), and is best adapted to cold, oxygen-rich water. It is arguably the largest octopus species, based on a scientific record of a 71 kg (156 lb) individual weighed live. The alternative contender is the seven-arm octopus (Haliphron atlanticus) based on a 61 kg (134 lb) carcass estimated to have a live mass of 75 kg (165 lb). However, a number of questionable size records would suggest E. dofleini is the largest of all octopus species by a considerable margin.

E. dofleini commonly prey upon shrimp, crabs, scallops, abalone, clams, lobsters and fish. Food is procured with its suckers and then bitten using its tough "beak" of chitin. They have also been observed to catch spiny dogfish (Squalus acanthias) up to four feet in length while in captivity. Additionally, consumed carcasses of this same shark species have been found in giant Pacific octopus middens in the wild, providing strong evidence of these octopuses preying on small sharks in their natural habitat.

Octopuses are ranked as the most intelligent invertebrates. In the third century CE, Roman natural historian Claudius Aelianus wrote: "Mischief and craft are plainly seen to be the characteristics of this creature." Giant Pacific octopuses are commonly kept on display at aquariums due to their size and interesting physiology, and have demonstrated the ability to recognize humans that they frequently come in contact with. These responses include jetting water, changing body texture, and other behaviors that are consistently demonstrated to specific individuals. They have the ability to solve simple puzzles, open childproof bottles and use "tools". The octopus brain has folded lobes (a distinct characteristic of complexity), visual and tactile memory centers. They have about 300 million neurons. They have been known to open tank valves, disassemble expensive equipment and generally wreak havoc in labs and aquariums. Some researchers even claim that they are capable of motor play and having personalities. Some claim that octopuses are psychic, as Paul was made famous by predicting all seven winning teams in the 2010 FIFA World Cup, although this is not scientifically supported.