Native American Millennium Challenge Demonstration Act This bill requires the Department of the Interior to establish the Native American Millennium Challenge Demonstration Project to provide economic development assistance for Native Americans. Entities must enter into a five-year binding agreement with the United States to receive assistance. Among other elements, these agreements must contain a description of the specific objectives related to sustainable economic development and poverty reduction that the entity expects to achieve. Assistance shall be provided in the form of funding agreements and may not be provided as loans. Additionally, funds may not be used for regulated gaming activities.