The Treaty of Washington (1831) was a treaty between the Menominee (an American Indian tribe) and the United States Government. The treaty was initially made and signed on February 8, 1831 in Washington, D.C.. In the treaty, the Menominee ceded about 2,500,000 acres (10,000 km2; 3,900 sq mi) of their land in Wisconsin primarily adjacent to Lake Michigan. During the ratification of the treaty in June 1832, the United States Senate modified the treaty to provide additional land for the . The Menominee Tribe did not agree to the changes, and the treaty was renegotiated on October 27, 1832 to resolve the differences. These two treaties are commonly referred to singularly as the Treaty of Washington.
The treaty was first brought about by Colonel Samuel C. Stambaugh, the Indian agent at Green Bay. The principal Menonminee Chief was Oshkosh, who did not attend the treaty negotiation due to his belief that without his presence, the treaty would not be binding on the tribe. The head chief that attended the talks for the tribe was Iometah, who was shown signing the treaty as Aya-mah-taw, while the United States was represented by John H. Eaton, the Secretary of War. The negotiations concluded on February 8, 1831, ceding 2,500,000 acres (10,000 km2; 3,900 sq mi) to the United States in return for clothing, provisions and annuities totaling approximately US$92,000. In addition, approximately 500,000 acres (2,000 km2; 780 sq mi) were to be transferred to the Stockbridge-Munsee tribe for which the Menominee were to be paid an additional US$20,000.
In the winter of 1831, a group of Indians including Oneida chief Daniel Bread travelled to Washington to protest the treaty, which had bypassed the interests of the Oneida people. President Andrew Jackson agreed to adjust the assignment of lands to the Oneida in response.