Nonintercourse Act, an act passed by the United States Congress in 1809. The act arose out of British and French seizure of American ships and sailors during the Napoleonic Wars, when each country was trying to cut off the other from foreign trade. It forbade the exporting and importing of all goods to or from Great Britain and France, or the lands they controlled. The act provided for resumption of trade with either country if it agreed to respect the rights of American shipping.

The Nonintercourse Act failed to induce Britain or France to respect American rights, and it had a disastrous effect on American trade. When it expired in 1810, it was replaced by Macon's Bill No. 2, which reopened all trade but provided that should either Britain or France cease interference with American shipping, trade with the other would be halted unless it also ceased interference within three months. President Madison, misled by Emperor Napoleon I, on November 2, 1810, proclaimed that France was ceasing its interference. Britain did not change its policies, and accordingly on March 2, 1811, Congress reimposed restrictions on trade with Britain.

Even though the French continued to interfere with American shipping, American anger remained directed at Great Britain, and on June 18, 1812, the United States declared war on that country.