Mbayá, South American Indians of the Argentine, Paraguayan, and Brazilian Chaco, speakers of a Guaycuruan language. At their peak of expansion, they lived throughout the area between the Bermejo and Pilcomayo rivers in the eastern Chaco. At one time nomadic hunters and gatherers, the Mbayá became feared warlike horsemen shortly after they encountered the Spanish and their horses.
The pre-Spanish, pre-horse Mbayá had already given up their primary dependence on hunting, gathering, and horticulture and relied on tribute extracted from the Guaná, groups of settled agriculturalists whom the Mbayá had conquered. The Guaná, successful farmers, weavers, and potters, provided the Mbayá with labour, agricultural produce, and manufactured goods; the Mbayá, in turn, protected the Guaná from other predatory Chaco tribes.
The Mbayá first became familiar with horses during the late 16th and early 17th centuries, when the Spanish were expanding from their coastal strongholds into the interior reaches of the Gran Chaco. By the mid-17th century, less than 100 years after the arrival of the Spanish, the Mbayá had become skilled horsemen, and their culture was undergoing drastic changes. The range and intensity of their raids on Spanish and Indian villages alike increased, Mbayá horsemen expanded the variety and quantity of game animals that they hunted, and they were able to raid herds of Spanish cattle and horses more effectively. Mbayá society became more stratified than it had been in the pre-horse days.
The 20th-century Mbayá are sedentary farmers, noted for their elaborately decorated pottery and textiles. They have intermarried with other Indians and with non-Indians and have become acculturated to the rural societies in which they live.