This essay introduces four volumes of published articles exploringdifferent theories and practices of citizenship from ancient Greece to the present. This period has witnessed significant changes as to who can be a citizen, the topic of Volume 2, how we exercise citizenship – the rights and duties of citizenship and the practices through which we use them, examined in Volume 3, and where citizenship is located – the nature of the political community to which a citizen belongs, the subject of Volume 4. For example, much of the history of citizenship has involved the struggle for the inclusion of the propertyless, women and ethnic minorities into the fold of citizens. Likewise, the range of political rights and duties has altered over time, as have the degree and ways they need to be performed. In most countries, military service has ceased to be a core civic duty, while political participation has become increasingly limited to a voluntary and periodic act of voting for a decision-maker rather than regular and sustained direct involvement in decision-making. The type of political community deemed to sustain a form of citizenship has also evolved, expanding beyond the city to encompass nation states, empires, and international bodies such as the EU.