The formation of coalitions to achieve both collaborative and competitive goals is a phenomenon we see all around us. The list is long and varied: production cartels, political lobbies, customs unions, environmental coalitions, and ethnic alliances are just a few everyday instances. Drawing upon and extending his inaugural Lipsey Lectures at the University of Essex, Debraj Ray looks at coalition formation from the perspective of game theory. How are agreements determined? Which coalitions will form? And are such agreements invariably efficient from a social perspective? Ray brings together developments in both cooperative and noncooperative game theory to study the analytics of coalition formation and binding agreements. This book concentrates on pure theory, but discusses several potential applications, such as oligopoly and the provision of public goods.