The Treaty of Fort Stanwix was an important treaty between North American Indians and the British Empire. It was signed at in 1768 at Fort Stanwix, located in present-day Rome, New York. It was negotiated between Sir William Johnson and representatives of the Six Nations (the Iroquois).

The purpose of the conference was to adjust the boundary line between Indian lands and British colonial settlements set forth in the Royal Proclamation of 1763. The British government hoped a new boundary line might bring an end to the rampant frontier violence, which had become costly and troublesome. Indians hoped a new, permanent line might hold back British colonial expansion.

The final treaty was signed on November 5 with one signatory for each of the Six Nations and in the presence of representatives from New Jersey, Virginia and Pennsylvania as well as Johnson. The Native American nations present received gifts and cash totalling £10,460 7s. 3d. sterling, the highest payment ever made from colonists to American Indians.Taylor, 44 The treaty established a Line of Property which extended the earlier proclamation line of the Alleghenies (the divide between the Ohio and coastal watersheds), much farther to the west. The line ran near Fort Pitt and followed the Ohio River as far as the Tennessee River, effectively ceding the Kentucky portion of the Colony of Virginia to the British, as well as most of what is now West Virginia.
Although the Six Nations of New York had previously recognised English rights southeast of the Ohio River at the 1752 Treaty of Logstown, they continued to claim ownership (by conquest) over all land as far south as the Tennessee River — which they still considered their boundary with the Cherokee and other "Southern" tribes. Although representatives of the Indian nations who actually occupied these lands, primarily the Shawnee and Lenape, were present at the negotiations in 1768, they were not signatories, and had no real role in the Iroquois' sale of their homeland. Rather than secure peace, the Fort Stanwix treaty helped set the stage for the next round of hostilities along the Ohio River, which would culminate in Dunmore's War.

The treaty also settled land claims between the Six Nations and the Penn family, the proprietors of Pennsylvania, where the lands acquired in 1768 were called the "New Purchase". Due to disputes about the physical boundaries of the settlement, however, the final treaty line would not be fully agreed upon for another five years.
thumb|left|Map showing the "New Purchase" of 1768 in Pennsylvania
The final portion of the Line of Property in Pennsylvania, called the Purchase line in that State, was fixed in 1773 by representatives from the Six Nations and Pennsylvania who met at a spot called Canoe Place at the confluence of West Branch of the Susquehanna River and Cush Cushion Creek in what is now Cherry Tree, Pennsylvania.

The reason for the Treaty of Fort Stanwix was that the press of population growth and economic development turned the attention of investors and land speculators to the area west of the Appalachians. In response to demands by settlers and speculators, British authorities were soon pressing the Iroquois and Cherokees for cessions of land in Indian country. The Treaty of Lochaber with the Cherokee followed in 1770, whereby the Cherokee withdrew their claim to part of the same country, encompassing the south part of present-day West Virginia. No longer able to play off rival colonial powers following the British victory in the French and Indian War, Indians were reduced to a choice between compliance and resistance. Weakened by the recent war, they negotiated away parcels of land in exchange for promises of protection from further encroachments. So in 1768, the Iroquois gave up their claim south of the Ohio, hoping thereby to deflect English settlement away from their own homeland.