The author re-examines the concept of equality in international society, past and present. The conventional view that equality of states necessarily flows from sovereignty, that it is a corollary to sovereignty or simply a synonym, is considered a contingent rather than a necessary contention. The main argument is that equality in global international society should be theorised anew, restoring the normative strength of the principle. It is shown how concepts of equality make intelligible different normative and ethical conceptions of the modern political space in the past. Drawing on the works of such diverse theorists as Hans Kelsen, Peter Singer, John Rawls and Michael Oakeshott, the author suggests how a renewed interest in equality contributes to making international society a more inclusive, egalitarian, and credible moral and political association.