St. Guinefort does not appear in the official canon of the Catholic Church. Or at least, not the Guinefort we're talking about here (St. Cucuphas is sometimes referred to as Guinefort). That's because Guinefort was a 13th-century dog, thought to be a greyhound. According to tradition, he belonged to St. Roch, but after his master's death went to live with a noble family near Neuville, France. And that's where he earned his sainthood.
While both the parents and the nurse were absent, a large serpent entered the house and approached the cradle. Guinefort, however, remained on guard. When Guinefort saw the serpent he attacked it and upset the cradle. The dog and serpent exchanged many bites but in the end Guinefort prevailed and tore the serpent to pieces leaving behind considerable blood and gore. Although injured, the dog remained on guard duty until the family returned.
The family panicked when they saw the gory scene. First the nurse came in and began screaming that the dog had devoured the child. The mother then ran in also thinking Guinefort had killed her child. The child’s father now quickly took action. He drew his sword and killed the dog. Only then did the family see the infant sleeping peacefully off to the side.
Having realized they unjustly had accused and killed Guinefort, the lord took the dog’s body and placed it in a well which he covered with stones. He also planted trees beside it to memorialize the dog’s deeds.
That's a good dog. Villagers started bringing their children to the shrine to pray to Guinefort for their protection, and the dog became locally known as a saint. The Catholic Church was not happy about that. There was even talk that such veneration was a downright pagan activity. The story of Guinefort may remind you of similar tales from all over, which are parables cautioning one against being too quick to judge others. Read the story of Guinefort and why he was made into a saint at the Ultimate History Project. -via Metafilter