A Greyhound is a dog breed that is skinny, has long legs, and runs faster than any other breed of dog. It is one of the oldest breeds of dogs. For centuries, people have raced them in some parts of the world. Greyhound racing is a bit like horse racing in many ways. In recent years, many Greyhounds have been mistreated or killed especially after they get too old to race, but many animal rights rescue groups try to stop that and to help them be adopted by people to keep as pets.