The domestic or fancy rat is descended from the Brown Rat (also known as the Norwegian Rat) and is thought to have originated from Asia moving into Europe in 1553 and then onto the US in 1775. It lives in burrows and is a good swimmer and can often be found inhabiting sewers.

There can be much prejudice against the rat due to the spread of plague, but it was the Black Rat that played a part in this epidemic and it was not the rat itself that carried the plague but the fleas that it carried.

In the early 1800s rats were kept, and bred and used for ratting contests where rats were released and terriers were competed as "rat catchers". In the late 1800s rats were bred in captivity for scientific research into nutrition, intelligence and disease and it was noted in the laboratories that the rat was highly suited as a pet due to its intelligence and tameness. By the late 1800s rats were kept in captivity as pets and by the early 1900s had become a popular pet. However, the keeping of rats as pets declined in later years due to the introduction of more "appealing" pets such as the hamster but the popularity of the rat as a pet is once again rising.