The brown rat, also known as the common rat, street rat, sewer rat, wharf rat, Hanover rat, Norway rat and Norwegian rat, is a widespread species of common rat. One of the largest muroids (a superfamily of rodents including mice, rats, voles, hamsters, lemmings, gerbils, and many other relatives), it is a brown or grey rodent with a body length of up to 28cm long, and a tail slightly shorter than that. It weighs between 140 and 500g. Thought to have originated in or around northern China, this rodent has now spread to all continents except Antarctica, and is the dominant rat in Europe and much of North America. Translocation of the rat was not generally intentional, but rats stowed away on ships and went ashore wherever the ship landed. With rare exceptions, the brown rat lives wherever humans live, particularly in urban areas. While they must have originated as a species capable of living without humans, nowadays they are only found within close proximity of humans.

Given its lack of true wild behaviour, this is not a species that I expect to write on, so I have not included a list of articles that it appears in, further more, this will not appear in a list of animals to try to see, unless someone knows of a truly wild brown rat region.