A sheepdog trial – also herding event, stock dog trial or simply dog trial — is a competition or test of the working abilities of dogs of herding breeds. It is a type of dog sport that emerged in the 1860s in New Zealand. By the 1870s regular trials were also being held in Australia and in the United Kingdom, and by the end of the twentieth century the sport had spread to many countries of the world. In competition, dogs demonstrate basic herding management skills assessed by the judge. These events are organised by international and national cynological and sports organisations and by associations of sheep- and cattle-breeders. Usually sheep are to be herded; other animals including ducks or cows may also be used.

A herding dog, also known as a stock dog or working dog, is a type of dog that either has been trained in herding livestock or belongs to one of the breeds that were developed for herding. A dog specifically trained to herd sheep is known as a sheep dog or shepherd dog.