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.

The Appenzeller Sennenhund is the traditional working dog of the Sennen – Alpine cattle-herders and dairymen^[2] – of the Appenzell region of north-eastern Switzerland. The earliest written description of it is that of Friedrich von Tschudi in Das Thierleben der Alpenwelt, published in 1853.^{[3][4]: 553} In the late nineteenth century Max Sieber, a forester who had seen the dogs at cattle shows in eastern Switzerland, asked the Schweizerische Kynologische Gesellschaft [de] to recognise the breed;^[5] a commission was established with financing from the canton of St. Gallen^[5] and the Appenzeller Sennenhund was recognised in either 1896^[6] or 1898.^[3][7]: 88 Eight of the dogs were shown at the international dog show in Winterthur in 1898; they were entered in a new Sennenhunde class.^[5]

In 1906 a breed society, the Appenzeller Sennenhunde Club, was established at the instigation of the cynologist Albert Heim, who in 1914 drew up the first full breed standard.^[5] It was definitively accepted by the Fédération Cynologique Internationale in 1954.^[8]

It has spread from Appenzell to other parts of Switzerland and to other European countries.^[3] A study published in 2004 found it to be the most-registered breed in the canton of Appenzell, with 259 out of a total of 1358 registrations in the canton, or about 19%; in the whole of Switzerland it accounted for 360 of a total of 33470, or about 1.1% of all dogs registered by the Schweizerische Kynologische Gesellschaft.^[9]: 226

It is the only Swiss dog breed considered to be at risk by ProSpecieRara, which lists it as gefährdet, 'endangered'. Numbers are stable but the gene pool is narrow; the association is in collaboration with the breed society, the Schweizerischer Club für Appenzeller Sennenhunde, to broaden it.^[1][10]

The Appenzeller Sennenhund is the third-largest of the Sennenhund or Swiss mountain dog group, which also includes the Grosser Schweizer Sennenhund, the Berner Sennenhund or Bernese Mountain Dog, and the Entlebucher Sennenhund. It is a medium-sized dog: male dogs stand some 52–56 cm at the withers, bitches about 2 cm less;^[11] weights are in the range 22–32 kg.^[12]: 66

The coat is double, the top-coat thick, straight and glossy. It is always tricoloured: the principal colour may be either black or Havana brown, with white markings to the chest, face and feet, and reddish-brown areas between those and the base colour.^[11]

The tail is set high and is carried in a tight curl over the back when the animal is moving.^[11] The ears are set high and are triangular and fairly small; they hang close to the cheeks when the animal is at rest, and are raised and turned forward when it is alert.^[11] Among the faults that disqualify a dog from registration are a wall eye, a kinked tail, a single coat and a coat that is not three-coloured.^[7]: 88 Dogs may be expected to live for some 12–14 years.^[13]: 290

According to the breed standard, the Appenzeller Sennenhund is lively, high-spirited, athletic and suspicious of strangers.^[8][11]

The Appenzeller Sennenhund was traditionally used by the Alpine cattle-herders and dairymen of the Appenzell region both to herd cattle and to guard property.^[3] It is often kept as a companion dog.^[3]