The Report of 1800 was a resolution drafted by James Madison arguing for the sovereignty of the individual states under the United States Constitution and against the Alien and Sedition Acts. Adopted by the Virginia General Assembly in January 1800, the Report amends arguments from the 1798 Virginia Resolutions and attempts to resolve contemporary criticisms against the Resolutions. The Report was the last important explication of the Constitution produced before the 1817 Bonus Bill veto message by Madison, who has come to be regarded as the "Father of the Constitution."

The arguments made in the Resolutions and the Report were later used frequently during the nullification crisis of 1832, when South Carolina declared federal tariffs to be unconstitutional and void within the state. Madison rejected the concept of nullification and the notion that his arguments supported such a practice. Whether Madison's theory of Republicanism really supported the nullification movement, and more broadly whether the ideas he expressed between 1798 and 1800 are consistent with his work before and after this period, are the main questions surrounding the Report in the modern literature.