This article explores the phenomenon of internationalist public ritual between 1919 and the mid 1950s. It aims to fill a notable gap in the existing literature on interwar peace activism by demonstrating how British supporters of the League of Nations made extensive use of public ritual to communicate to a mass electorate key liberal-internationalist ideas concerning global interdependence, international government and world citizenship. More ambitiously, it argues that through public ritual these ideas became part of the symbolic resources available to British people as they sought to make sense of their relationship to the imperial nation-state and to the broader geopolitical transformations set in train by the Second World War. Demonstrating how League-themed ritual became embedded within existing civic traditions across the political spectrum, the analysis argues that the belief that Britain belonged to – and owed certain duties towards – an imagined international community became more central to popular representations of national identity than at any time previously. Internationalist public ritual was in its heyday between 1920 and 1936; thereafter domestic controversies over foreign policy led to the loss of much of the tradition's ‘civic’ character and League-themed ritual became increasingly implicated in the oppositional political theatre of the left. As the final section of the article shows, the internationalist tradition experienced something of a revival immediately after the Second World War, bolstered by idealism surrounding the establishment of the United Nations. Yet by the mid 1950s this tradition was once more displaying distinct signs of decay, a consequence of further shifts in the meaning of national identity brought about by the new global polarities of the Cold War.