The County of Mortain was a medieval county in the Duchy of Normandy in France centered on the town of Mortain, disputed between France and England during parts of the Hundred Years' War. A choice landholding, usually either kept within the family of the duke of Normandy (or the king of France) or granted to a noble in return for service and favor. This was the main reason Mortain had so many counts and from different lineages, as shown below, during its long history.
↑There are apparently few certain facts about William Warlenc, who was deprived of the County to the benefit of Robert (sometimes said to have been c.1055).