August 22 is the Feast Day of the only (to my knowledge) Dog Saint. Guinefort was a 13th-century French dog that received local veneration as a folk saint after miracles were reported at his grave.

Guinefort the greyhoud belonged to a knight who lived in a castle near Lyon. One day, the knight went hunting, leaving his infant son in the care of Guinefort. When he returned, he found the nursery in chaos – the cot was overturned, the child was nowhere to be seen and Guinefort greeted his master with bloody jaws.

Believing Guinefort to have devoured his son, the knight slew the dog. He then heard a child crying. He turned over the cot and found his son lying there, safe and sound, along with the body of a viper. Guinefort had killed the snake and saved the child.

On realizing the mistake the family dropped the dog down a well, covered it with stones and planted trees around it, setting up a shrine for Guinefort. Guinefort became recognised by locals as a saint for the protection of infants. It was alleged by contemporary commentators that locals left their babies at the site to be healed by the dog.

Taken from Wikipedia.