Octopuses have become a touchstone in debates about invertebrate sentience. A review of the evidence clarifies what is known, what is uncertain, and what the welfare implications are.
Octopus sentience evidence is now compelling enough to demand serious welfare consideration. The precautionary principle — applied in the absence of certainty — is clearly warranted given the combination of neurological complexity, flexible learning, tool use, individual personalities, and pain responses. The UK government included cephalopods in the Animal Welfare (Sentience) Act 2022, reflecting the scientific consensus. Practical welfare implications include: octopuses should not be farmed commercially until humane killing and housing methods are established, research use should be minimised and refined, and individual octopuses should be enriched and socially isolated (as appropriate for a solitary species) in captivity.