There is no single "tamest" horse breed. Temperament depends on breed, individual personality, training, handling, and environment. While some breeds like the American Quarter Horse or Morgan are often calm, individual horses vary widely.
Choosing the Right Horse
Even the calmest horse is a prey animal and can react unpredictably to perceived threats. Focus on finding a horse with a temperament suited to your experience level, solid training, and a lifestyle match for your riding goals.