The Welsh Terrier is a dog breed, one of many Terrier breeds. The Welsh Terrier originates from Wales and has existed since the 1800s. Its origins lie in the Old English Black and Tan terrier that existed in England as early as the 13th century. It also existed in Wales and it was that sort that finally was registered by The Kennel Club under the name Welsh terrier. Until 1900, it was called the "Old English Terrier" or "Black and Tan Rough Haired Terrier". The breed has been recognised since 1886 and is more common than the Airedale Terrier or the Fox Terrier.

The Welsh Terrier is a consummate terrier—a terrier in a nutshell—with a typical terrier temper. It is not recommended as a first dog in general, because it demands an owner who is steady and knowledgeable. In the right hands, it is a happy, lively, and seldom shy or timid dog. Dogs of this breed can be devoted and obedient friends and can function either as city dogs or as country dogs. Some Welshies exhibit a typical hunting instinct. A Welsh Terrier does not demand lots of physical exercise, but it hardly ever becomes tired and is a true comrade for the one who likes open-air activities. It is active and intrepid and not eager to fight, although it will hold its own when necessary. The Welshie needs a lot of intellectual stimulation to stay agreeable. A small yard to walk all day long, without any other activities, is not enough. These dogs need interesting things to do each day.

Welsh Terriers get along well with children; they love to play and to follow a child as it plays. These terriers love playing with children, but sometimes the child gets tired before the dog, so adult supervision is required to prevent misunderstandings.

The Welsh Terrier is suited to fox hunting and for being kept as a pet. This breed is colored black and tan. They can grow up to 39cm (15 in.) with a weight of 9 kg (20 lb).

The fur contains two layers, an undercoat that insulates and abrasive fur on top that protect against dirt, rain, and wind. The color is red-brown with black marks. White is allowed only as small marks on the front of the breast.

This breed is a so-called trimming breed; it has abrasive hair that has to be trimmed—not cut! However, it does not shed its fur as many other dog breeds do. This dog does not need constant bathing. The fur must be trimmed about every third month. A complete trimming takes three to four hours and the breeder should give tip about where the dog can get trimmed by a professional (in the correct way so that the fur is not destroyed).

The body of the Welsh Terrier is normal and healthy so that the physique is durable and lasting. There are no known defects related to the breed. A healthy Welsh Terrier lives about 15 years on average and stays active and alert up to a high age if it is well taken care of and healthy.