The largest litter ever recorded (so far) was born to a Neapolitan Mastiff and there were 24 pups born in total (although 3 died shortly). The record for the largest litter when all the pups survived stands with 3 different dogs at 23 pups. Those dogs were an American Foxhound, a St. Bernard, and a Great Dane. I am not sure which dogs have the largest litters on average, I'm pretty sure it just varies from dog to dog.