The Pyrenean Mountain Dog (Chien de Montagne des Pyrénées) is a French breed of livestock guardian dog. In France, it is commonly called the Patou. It is known as the Great Pyrenees in the US. The breed originates from the eastern or French side of the Pyrenees Mountains (which separate France and Spain). It is recognised as a separate breed from the Mastín del Pirineo or Pyrenean Mastiff from the Spanish side of the mountains, but they are closely related.
The Patou is widely used throughout France as a livestock guardian, particularly in the French Alps and the Pyrenees, protecting flocks from predation by wolves and bears. In the US, it is also used to protect flocks from various predators.
Image credit: HeartSpoon, CC BY-SA 4.0
Adapted from Wikipedia, CC BY-SA 4.0 — https://en.wikipedia.org/wiki/Pyrenean_Mountain_Dog