Onychectomy, popularly known as declawing, is an operation to remove an animal's claws surgically by means of the amputation of all or part of the distal phalanges, or end bones, of the animal's toes. Because the claw develops from germinal tissue within the third phalanx, amputation of the bone is necessary to fully remove the claw. The terms onychectomy and declawing imply mere claw removal, but a more appropriate description would be phalangectomy, excision of toe bone.

Numerous procedures performed on domestic animals are usually more invasive than purely cosmetic alterations, but differ from types of veterinary surgery that are performed exclusively for urgent health reasons. Such procedures have been grouped together under the technical term 'mutilatory' by the Royal College of Veterinary Surgeons in a report describing the reasons for their being conducted and their welfare consequences, and by others.