Dogs are the canine companions who have shared our lives for millennia. Ranging from tiny Chihuahuas to enormous Great Danes and every breed and magnificent mutt in between. Dogs are an incredibly diverse species.

The dog is a domesticated descendant of the wolf called the domestic dog. It is derived from an ancient, extinct wolf, and the modern wolf is the dog's nearest living relative. The dog was the first species to be domesticated, by hunter-gatherers over 15,000 years ago, before the development of agriculture.

There are at least 800 breeds (kinds) of dogs. Dogs whose parents were the same breed will also be that breed: these dogs are called purebred or pure pedigree dogs. Dogs with parents from different breeds no longer belong to one breed: they are called mutts, mixed-breed dogs, hybrids, or mongrels.

Dogs are known to help relieve stress and anxiety and improve health and wellbeing in people. Around 40% of US households are estimated to have one or more dogs.