The Estrela Mountain Dog (Cão da Serra da Estrela) is reputed to be one ofthe oldest breeds of the Iberian Peninsula and is of ancient origins but we actually haven’t any concrete information about the origin of the breed.

One theory is that during the migration of Romans or Visigoth, there where introduced big dogs coming from the Tibetan Highland and give origin at all the similar breed like the mountain dog of Caucasus, Sarplaninac etc. These flock stock guarding dogs where used to protect sheep and cattle, especially in mountain regions and accompanying the shepherd with its flock to defend them against wolves and thieves.
The Estrela Mountain Dog originates from the Estrela Mountain region, in the centre-east of Portugal. Centuries ago, travel in the mountain region was difficult and the breed was kept fairly pure by the use of dogs that occurred only locally.
The development of the breed was in the hands of the local farmers who highly prized the dogs' guarding ability; only dogs who excelled in guarding were kept and bred from. The Estrela had to be capable of dealing with a full-grown wolf, and so it developed into a strong, powerful, supple, and agile dog, conveying an impression of vigour and strength.
The Estrela is a very agile breed and is capable of moving easily over rough terrain and in times before the wolf was wiped out, they often wore spiked metal collars to protect them against attack.
The Estrela was often left to independently guard the flock in the mountains, whilst the shepherd went into the village.
Note that the Estrela is a flock guard dog and not a herding dog.
The breed has powerful jaw-bones and strong teeth. The coat is dense with a special thick tuft of hair around the throat which serves as a defence to protect it from the jaws of the enemy, the wolf. The ears are small, folded and carried back so as to keep them out of the way.
To protect him from the extremes of the weather in which he had to live out for long periods, he grew a thick, dense coat. Originally it probably was fairly short and through the times it evolved to two varieties: there is a long and short haired variety.
During the 1930s, Portugal underwent a revival of interest in their native breeds, and produced the first breed standard for the Estrela in 1933.