This article challenges prevailing national interpretations of solidarity by examining its colonial dimensions. Employing the Durkheimian school as a historical lens, I demonstrate how the colonial context during the Third Republic shaped the emergence and application of solidarity as a scientific concept. Informed by colonial ethnographies, solidarity was not merely a sociological self-description within European nations; it also formed part of political agendas beyond Europe. I illustrate how Durkheim’s concept was utilized to enhance scientific understanding of colonized societies, aiding French colonial administrators in promoting developmentalist reforms. As national models extended internationally, solidarity evolved from social cohesion to economic integration within the international legal order. This progression toward modern solidarity—and the injustices it entailed—appeared inevitable, masking political struggles for self-determination. By critically recontextualizing solidarity, this analysis contributes to contemporary political theory debates, demonstrating its application in supporting an inclusive legal-economic agenda while failing to systematically confront colonial injustices.