The Beaver Wars (Mohawk: Tsianì kayonkwere), also known as the Iroquois Wars or the French and Iroquois Wars (French: Guerres franco-iroquoises) were a series of conflicts fought intermittently during the 17th century in North America throughout the Saint Lawrence River valley in Canada and the lower Great Lakes region which pitted the Iroquois against the Hurons, northern Algonquians and their French allies. As a result of this conflict, the Iroquois destroyed several confederacies and tribes through warfare: the Hurons or Wendat, Erie, Neutral, Wenro, Petun, Susquehannock, Mahican and northern Algonquins whom they defeated and dispersed, some fleeing to neighboring peoples and others assimilated, routed, or killed.

The Iroquois sought to expand their territory and to monopolize the fur trade with European markets. They originally were a confederacy of the Mohawk, Oneida, Onondaga, Cayuga, and Seneca tribes inhabiting the lands in what is now Upstate New York along the shores of Lake Ontario east to Lake Champlain and Lake George on the Hudson river, and the lower-estuary of the Saint Lawrence River. The Iroquois Confederation led by the Mohawks mobilized against the largely Algonquian-speaking tribes and Iroquoian-speaking Huron and related tribes of the Great Lakes region. The Iroquois were supplied with arms by their Dutch and English trading partners; the Algonquians and Hurons were backed by the French, their chief trading partner.

The Iroquois effectively destroyed several large tribal confederacies, including the Mohicans, Huron (Wyandot), Neutral, Erie, Susquehannock (Conestoga), and northern Algonquins, with the extreme brutality and exterminatory nature of the mode of warfare practised by the Iroquois causing some historians to label these wars as acts of genocide committed by the Iroquois Confederacy. They became dominant in the region and enlarged their territory, realigning the American tribal geography. The Iroquois gained control of the New England frontier and Ohio River valley lands as hunting ground from about 1670 onward.

Both Algonquian and Iroquoian societies were greatly disrupted by these wars. The conflict subsided when the Iroquois lost their Dutch allies in the colony of New Netherland after the English took it over in 1664, along with Fort Amsterdam and the town of New Amsterdam on the island of Manhattan. The French then attempted to gain the Iroquois as an ally against the English, but the Iroquois refused to break their alliance, and frequently fought against the French in the 18th century. The Anglo-Iroquois alliance would reach its zenith during the French and Indian War of 1754, which saw the French being largely expelled from North America.

The wars and subsequent commercial trapping of beavers was devastating to the local beaver population. Trapping continued to spread across North America, extirpating or severely reducing populations across the continent. The natural ecosystems that came to rely on the beavers for dams, water and other vital needs were also devastated leading to ecological destruction, environmental change, and drought in certain areas. Beaver populations in North America would take centuries to recover in some areas, while others would never recover.