The Great Pyrenees is a very old breed that has been used for hundreds of years by shepherds, including those of the Basque people, who inhabit parts of the region in and around the Pyrenees Mountains of southern France and northern Spain (specifically Aragon and Navarre).
Varro, a Roman author who lived in the first century BC, wrote in his treatise of rural economy "De re rustica" in 37 BC.:
"The dog is essential for those who raise animals for wool. It is the guardian of livestock in general but is the natural defender of the sheep and goats. The wolf lurks constantly and we oppose it with the dogs"... "As for its appearance, choose those who are well-trained, large size, with black or red eyes, the nose of the same color, red lips pulling to black, not too collected, nor too pendants"... "It is equally essential that the dogs have strong head, long, floppy ears, wide and short neck, thighs and rights more inwardly turned than out, wide legs, fingers apart, hard nails and bent, spine nor projection nor convex, bushy tail, sonorous voice, good match muzzle and preferably with white hair so that it can be easily distinguished from wild animals at night."
One of the first descriptions of the breed dates from 1407, Fray Miguel Agustín, "prior" of the Temple who lived between 1560 and 1630, published in 1617 in Catalan (the first edition appeared in Spanish in 1622), a book which he called Libro de los secretos de la agricultura, casa de campo y pastoril. It gives the reasons why shepherds prefer white puppies, excluding those born with spots of dark color. Relates the friar: "The wool cattle dogs should not must be so big or so heavy as those of the guard of the house, but strong and sturdy, lightweight and ready to combat and fight and for run, because they have to make saves and guard against wolves and hunt them down if those take a cattle... These should be white so that the shepherd can easily see when these run after the wolf and know them in the evening and the morning." From 1675 the breed was a favorite of The Grand Dauphin and other members of the French aristocracy. In the mid-19th century, the breed was not homogenized.