A police dog is a dog that is trained specifically to assist police and similar law-enforcement personnel with their work. Police dogs are often referred to by the term K9, which is a homophone of the term canine, a word that generally refers to the dog and its relatives.

In many jurisdictions the intentional injury or killing of a police dog is a felony, subjecting the perpetrator to harsher penalties than the statutes embodied in local animal cruelty laws.A growing number of forces outfit dogs with bulletproof vests and some even go so far as to make the dogs sworn officers, with their own police badges and IDs. Furthermore, a police dog killed in the line of duty is often given a full police funeral