This chapter deals with institutions and states. Institutions are essentially regular patterns of behaviour that provide stability and predictability to social life. Some institutions are informal, with no formally laid down rules such as the family, social classes, and kinship groups. Others are more formalized, having codified rules and organization. Examples include governments, parties, bureaucracies, legislatures, constitutions, and law courts. The state is defined as sovereign, with institutions that are public. After discussing the concept of institutions and the range of factors that structure political behaviour, the chapter considers the multi-faceted concept of the state. It then looks at the history of how the European type of state and the European state system spread around the world between the seventeenth and twentieth centuries. It also examines the modern state and some of the differences between strong states, weak states, and democratic states.