Cephalopod intelligence is a measure of the cognitive ability of the cephalopod class of molluscs.

Intelligence is generally defined as the process of acquiring, storing, retrieving, combining, and comparing information and skills. Though these criteria are difficult to measure in nonhuman animals, cephalopods are the most intelligent invertebrates. The study of cephalopod intelligence also has an important comparative aspect in the broader understanding of animal cognition because it relies on a nervous system that is fundamentally different from that of vertebrates. In particular, the Coleoidea subclass (cuttlefish, squid, and octopuses) is thought to contain the most intelligent invertebrates. It is also thought to be an important example of advanced cognitive evolution in animals, though nautilus intelligence is also a subject of growing interest among zoologists.

The scope of cephalopod intelligence and learning capability is controversial within the biological community, complicated by the inherent complexity of quantifying non-vertebrate intelligence. In spite of this, the existence of impressive spatial learning capacity, navigational abilities, and predatory techniques in cephalopods is widely acknowledged. Cephalopods are legally classified as being at least as sentient as vertebrates in some countries and have been compared to intelligent extraterrestrials, due to their convergently evolved mammal-like intelligence.

Cephalopods have large, well-developed brains, and their brain-to-body mass ratio is the among the largest of all invertebrates, falling between that of endothermic and ectothermic vertebrates. The large nerve fibers of the cephalopod mantle have been widely used for many years as experimental material in neurophysiology; their large diameter (due to lack of a myelin sheath) makes them relatively easy to study compared with other animals. Unlike vertebrates, octopus arms have their own neurons, so they do not require input from their central brain to function. In fact, two-thirds of an octopus's neurons are in the nerve cords of its arms. These are capable of complex reflex actions without input from the brain.

Unlike most other molluscs, all cephalopods are active predators (with the possible exceptions of the Bigfin squid and vampire squid). Their need to locate and capture their prey has likely been the driving force behind the development of their intelligence.

Crabs, the favorite food source of most octopus species, present significant challenges with their powerful pincers and their potential to exhaust the cephalopod's respiration system from a prolonged pursuit. Because of these challenges, octopuses will sometimes seek out lobster traps and steal the bait inside. They are also known to climb aboard fishing boats and hide in the containers that hold dead or dying crabs.

Captive octopuses have also been known to climb out of their tanks, travel some distance, enter another aquarium to feed, and return to their own aquariums.

Although believed^{[by whom?]} to not be the most social of animals, some^[which?] cephalopods are highly social creatures. When isolated from their own kind, some species have been observed shoaling with fish.