The article explores the relationship between individualism and group affiliation in the context of self-tracking technology. Prior research establishes that self-tracking fosters both self-focus and collective interactions. The article proposes that Durkheim’s notion of the cult of the individual offers a lens to understand the interplay of individualism and group formation in self-tracking. The notion of the cult of the individual suggests that individualism can be a source of public gatherings. While Durkheim’s notion remained largely untested for over a century, this study aims to build upon Durkheim’s framework by operationalizing it using Collins’s interaction ritual theory. By operationalizing the cult of the individual as a specific form of interaction ritual, we can analyze the collective mechanisms at play within the Quantified Self movement. This group organizes a community of self-trackers who share personal data during public gatherings. The article explores these public gatherings by deciphering their video recordings. Quantified Self-individualist gatherings are constituted by the co-presence of self-focused people, presenting one after the other their personal data following a script, and defending individuals against profaning situations. Quantified Self gatherings formed a transnational interaction ritual chain in approximately 71 cities on four continents, confirming that individualist gatherings can achieve a wide diffusion. Therefore, this original operationalization of Durkheim’s notion of the cult of the individual illustrates its enduring relevance and potential for broader application.