This systematic literature review examines the evolving role of the Scrum Master in contemporary project management, addressing how this critical agile leadership position has transformed since its original conception. Guided by the PRISMA 2020 framework and employing a PICO-informed search strategy, this study synthesized qualitative insights from peer-reviewed academic and grey literature published between 2010 and 2025. Thematic analysis revealed five major themes characterizing the role's evolution. First, the Scrum Master maintains a foundational identity as a servant leader who facilitates self-organization, though this ideal often conflicts with organizational pressures. Second, the role has expanded beyond its original scope to encompass coordination across scaled agile environments, global distributed teams, and remote work contexts. Third, Scrum Masters function as cultural catalysts who build organizational trust rather than merely managing processes. Fourth, role hybridization has emerged as a prevalent pattern, with Scrum Masters frequently assuming project management responsibilities that create accountability conflicts. Fifth, professionalization through structured competency frameworks and mentorship programs reflects the discipline's maturation, though gaps remain in practitioner supply and diversity. These findings reveal that while servant leadership orientation remains theoretically consistent, practical enactment varies substantially based on organizational maturity and structural clarity. The review identifies implications for organizations optimizing agile transformation, including the need for clear role boundaries and recognition of the Scrum Master as an organizational change agent. Future research should employ longitudinal designs and address diversity dimensions within the profession.