The Appenzeller Sennenhund is a Swiss breed of medium-sized working dog. It originates in the Appenzell region of north-eastern Switzerland, and is one of four regional breeds of Sennenhund or Swiss mountain dog, all of which are characterised by a distinctive tricolour coat.

Appenzell was a canton in the northeast of Switzerland, and entirely surrounded by the canton of St. Gallen, in existence from 1403 to 1597.