World federalism or global federalism is a political ideology advocating a democratic, federal world government. A world federation would have authority on issues of global reach, while the members of such a federation would retain authority over local and national issues. The overall sovereignty over the world population would largely reside in the federal government.

Federalism is a mode of government that combines a general government with regional governments in a single political system, dividing the powers between the two. Johannes Althusius is considered the father of modern federalism along with Montesquieu. Althusius notably exposes the bases of this political philosophy in Politica Methodice Digesta, Atque Exemplis Sacris et Profanis Illustrata (1603). In the Spirit of the Laws, Montesquieu for his part sees examples of federalist republics in corporate societies, the polis bringing together villages, and the cities themselves forming confederations. Federalism in the modern era was first adopted in the unions of states during the Old Swiss Confederacy.