A Dandie Dinmont Terrier is a small Scottish dog breed in the terrier family. The breed has a very long body, short legs, and a distinctive topknot of hair on the head. They are friendly but tough, and are suitable for interaction with older children. There are breed-specific health concerns: they can be affected by spinal problems due to their elongated body, and the breed is affected by canine cancer at a higher than average rate.

The breed is named after a fictional character in Sir Walter Scott's novel, Guy Mannering. This character, Dandie Dinmont, is thought to be partly based on James Davidson, who is credited as the originator of the modern breed. Davidson's dogs descended from earlier terrier-owning families, including the Allans of Holystone, Northumberland.

There are three breed clubs in the UK supporting the breed, although it is registered as a Vulnerable Native Breed by the Kennel Club due to its low number of puppy registrations per year.