Publius was the pen name used by the authors of the Federalist Papers.
Alexander Hamilton, James Madison, and John Jay published the essays under the shared pseudonym “Publius” while arguing for ratification of the proposed U.S. Constitution. The essays appeared primarily in New York newspapers from 1787 to 1788.
Hamilton wrote the largest number of essays, Madison wrote many of the most influential ones, and Jay contributed five before illness limited his participation. The shared name allowed the arguments to be presented as a coordinated defense of the Constitution rather than as a series of separate personal campaigns.
The Federalist Papers were originally published anonymously, so identifying authorship required later evidence and scholarly analysis. The essays are not the Constitution itself and were not official government commentary, but courts, historians, and political writers often consult them when discussing the Constitution’s intended structure and meaning.