The Federalist Papers were a series of 85 essays written by Alexander Hamilton, John Jay, and James Madison between October 1787 and May 1788 to urge New Yorkers to ratify the proposed United States Constitution, which was drafted in Philadelphia in the summer of 1787. The essays were published anonymously, under the pen name "Publius," in various New York state newspapers of the time. The collection was commonly known as The Federalist until the name The Federalist Papers emerged in the twentieth century.

Publius was the pseudonym used by Alexander Hamilton, James Madison, and John Jay to promote the ratification of the Constitution of the United States. Publius was a fairly common praenomen (the first or personal name of an ancient Roman) and most readers probably recognized “Publius” as Publius Valerius Publicola, a Roman patriot, general, and statesman who lived in the sixth century B.C.E. and who, according to Plutarch’s Lives, saved the early Roman republic several times from tyranny and military subjugation. It was in the light of the lessons of this Roman history that Hamilton, Madison, and Jay used “Publius” as their nom de plume for The Federalist, though Hamilton apparently made the initial choice, having already used “Publius” in 1778.