A classic livestock guardian dog, the Spanish Mastiff (also known as Spanish Mastin) originated from Spain. It is believed to have descended from Greek dogs and is similar in many ways to its cousin, the Anatolian Shepherd Dog. It is the heaviest of all livestock guardian dog breeds and is the largest of all the Spanish native dog breeds. It weighs from 145 to 220 pounds (with some males growing to as much as 265 pounds) and has a height range of 28 to 35 inches. There are two varieties of the Spanish Mastiff: the heavier mountain type found in the northern regions of Spain called the Mastin Pesado; and the Mastin Ligero which is the lighter variety and is more commonly found in the south and central parts of the country. This large and rustic breed has a massive head with a deep muzzle, strong jaws and a distinct double dewlap on the neck. It has small eyes, ears that are pendant and a fringed tail that is carried low. The coat is short, straight and has a dense undercoat. The typical coat colour is reddish or fawn.
This hardworking breed has a very dignified and independent nature. They are not very demonstrative of their affection even to their owner and family but in spite of this they are very loyal. As guardians, they are highly territorial and will be wary of anyone who enters the house. Despite their size, they are quick and agile. They are assertive (but not aggressive) and will not back down if challenged by another dog. Like other large breeds, they are prone to hip dysplasia, bloating and heart problems.