The Sealyham Terrier is a dog breed, one of many Terrier breeds. The Sealyham Terrier originates from England and was bred by crossing Basset Hounds, Bull Terriers, the Fox Terrier, the West Highland White Terrier, and the Dandie Dinmont Terrier.

The first Sealyham Terrier's club was created in 1908 and the breed was officially recognized in 1910. Sealyham Terriers are today found mainly in England and South Africa.

The Sealyham Terrier is an intelligent and charming dog, usually colored white, possibly with badger marking on the head. They grow up to 30cm with a weight of up to 9 kg.