This article argues that increasing demands in world public opinion for legitimate and effective international institutions require a paradigm shift in public international law. There is a part of public international law that should be better understood as international public law because it enables and disciplines the pursuit of public interests by international institutions. We consider such activities as exercises of international public authority. The article elaborates our approach by way of a thorough discussion of other approaches to governance phenomena in international legal scholarship. It then carves out the notion of international public authority. This notion includes various types of soft and informal governance instruments with innovative compliance mechanisms as well as the activities of informal and hybrid institutions or network-like structures.