The Federalist Papers are a collection of 85 articles and essays written by Alexander Hamilton, James Madison, and John Jay in the late 18th century. They were published to promote the ratification of the United States Constitution, explaining its principles, the necessity of a strong federal government, and addressing concerns raised by opponents. The essays provide insights into the framers' intentions and the foundational ideas of American democracy. They remain a critical source for understanding the Constitution and American political theory.