Fighting dogs have been found in Japan for centuries, and there are descriptions of large fighters in the 1300's from the island Tosa. These dogs were crossed with western dogs and it was from these hybrids that the japanese mastiff sprung. It is said that the breeds included are english bulldog (introduced in 1872), mastiff (1874), german pointer (1876) and great dane (1924). These dogs were later crossed with akitas and bull terriers.

The early tosa fights were quite different from the ones we are used to. The dogs were not allowed to hurt each other, and some fights took place with the dogs muzzled. Betting was not allowed either. The dogs competed in different classes depending on weight, and the tosa reached its peak in popularity in the early 1900's. The breed almost went extinct during the second world war, but today it is slowly growing in popularity.

The tosa should be a large and majestic dog, calm and brave. The head is broad with slight stop, rather long muzzle and small expressive eyes. The ears are small, set high and carried close to the head. The body should have a deep and long chest with straight back. Heavy boning, with straight frontlegs and slight angulation in hind. The tail is set high and long enough to reach the hock. The coat is short, hard and thick.