The Federalist Papers comprise 85 essays.
Alexander Hamilton, James Madison, and John Jay wrote the essays under the shared pseudonym Publius. They were published in New York newspapers from October 1787 through May 1788 to persuade readers to support ratification of the proposed Constitution.
The first 77 essays appeared serially during the ratification debate. A two-volume collection published in 1788 included those 77 essays plus eight additional pieces, bringing the recognized total to 85. Hamilton wrote the largest share, Madison contributed several influential essays, and Jay wrote the early essays before illness limited his participation.
The collection is often confused with the number of essays originally published in newspapers or with the authors' individual contributions. Federalist No. 10, by Madison, discusses factions, while Federalist No. 51 explains checks and balances. The essays were advocacy pieces, not official parts of the Constitution, but they remain a major source for understanding arguments made during ratification.