State formation is the process of the development of a centralized government structure in a situation in which one did not exist. State formation has been a study of many disciplines of the social sciences for a number of years, so much so that Jonathan Haas writes, "One of the favorite pastimes of social scientists over the course of the past century has been to theorize about the evolution of the world's great civilizations."
The study of state formation is divided generally into the study of ancient state formation (those that developed in stateless societies), medieval or early modern state formation, and the study of modern state formation (particularly of the form that developed in Europe in the 17th century and spread around the world). State formation can include state-building and nation-building.