Throughout much of the world, the concept of comity has played a fundamental role in shaping modern private international law. Sometimes labelled as a “principle”, sometimes as a “doctrine,” it provided the foundation and informed the evolution of several rules of conflict. Its importance, however, gradually faded as the field of private international law slid into the preserve of the national legislator. Scholarly attention to the subject followed suit, and private international lawyers have, by and large, dismissed it as a historical relic in the name of which courts would sometimes fine-tune the reach of their national substantive law and jurisdictional rules, refrain from questioning the lawfulness of another sovereign state’s acts, and restrict themselves from issuing such judgments and orders when to do so would have amounted to an unjustifiable interference. Comity, however, never really vanished: as Lord Collins of Mapesbury put it, “comity may be a discredited concept in the eyes of the text-writers, but it thrives in the judicial decisions” – in particular, in those of American courts. This conclusion is not entirely surprising: comity has long been acknowledged as a foundational principle of American conflict of laws. It had a complex and haphazard evolution in the continent, which is partly to blame for modern assessments of the concept as imprecise and confusing. Yet, while the term has come to be employed to refer to a variety of practices, these practices share “certain methods, values, and justificatory rhetoric.” The purpose of this study is to contribute to the elucidation of the notion of comity as it is understood in the United States – the jurisdiction where the greatest importance is attached to the concept. While other studies have examined this topic, they have mostly neglected to consider the phenomenon in a broader dimension and thus properly appraise the peculiarity of the American understanding of comity. It is submitted that this is particularly important insofar as the American understanding has affected the development of legal doctrines elsewhere, and stimulated further reflection on the role of the concept, especially when employed by prominent American scholars. This has in turn prompted the revitalisation of comity as a tool capable of alleviating problems of a global nature.