This thesis presents an investigation into the social media marketing strategies of luxury service brands. Specifically, the analysis explores how Michelin star restaurants in Ireland and the UK utilise social media platforms for the purposes of signalling their luxury status, with a specific focus on luxury brand authenticity, to consumers. To achieve this, participants within a total of 29 Michelin star restaurants across Ireland and the UK were interviewed over a nine-month period. Secondary analysis within this study stemming from an in-depth consultation of literature surrounding the central theoretical areas of the study culminated in the proposal of a novel theoretical framework depicting social media’s role within luxury organisations. In adopting a systematic literature review approach, the first major contribution of the thesis is the exhaustive analysis of the extant literature investigating the confluence of social media and luxury, a theoretical model illustrating the role of social media for luxury brand marketing, as well as a roadmap for future research in the area. This review was published in the International Journal of Management Reviews in 2022. In adopting a critical realist perspective and being grounded within a signalling theoretical foundation, the primary analysis of the study stems from the narratives of the participants, their depictions of their business and ascension to Michelin star status, the strategic objectives of their social media marketing strategies and how they utilise these platforms for signalling luxury and, in particular, authenticity. The perspectives sought included perceptions of the value of social media for luxury service brand marketing, exploration of the nature of relationships between luxury brand and consumer, as well as the most pertinent forms of content and its embedded elements which maximise social media’s signalling capacity. The live social media accounts of participants’ restaurants were also consulted to provide evidence of the varying forms of signals utilised by these brands. The study draws on the luxury services, social media marketing, and signalling theory literatures, culminating in the proposal of a taxonomy of eleven distinct signals of authenticity, further unpacked and discussed based on their degrees of tangibility/intangibility as well as their levels of implicitness/explicitness within luxury service brands’ social media content. In doing so, this study provides a more comprehensive understanding of the role of social media platforms in luxury service brand marketing strategies and the specificities of authenticity signals embedded within social media content for luxury service brands. The findings, interpretations, and conclusions make significant contributions to the fledgling luxury services literature as well as the maturing social media marketing literature and provides practical, actionable insights and recommendations for luxury service brand managers to further apply these contemporary technologies for strategic marketing purposes.