The growing demand for transparency and corporate accountability has transformed sustainability reporting into a strategic tool for managing legitimacy, especially considering the emergence of regulations such as Corporate Sustainability Reporting Directive (CSRD) and the standards of the International Sustainability Standards Board (ISSB). This study conducts a Systematic Literature Review (SLR) on the application of Legitimacy Theory to sustainability reporting between 2014 and 2024. Combining the PRISMA protocol with bibliometric and qualitative analyses, 51 scientific articles indexed in the Web of Science were analyzed. The results show a dual theoretical perspective of legitimacy: on the one hand, as institutional compliance and alignment with regulatory requirements; on the other, as a symbolic strategy to manage stakeholder perception, often through selective disclosure practices or greenwashing. The review also highlights a strong concentration of studies in European journals, a limited geographical and sectoral diversity, and a growing interest in digital mechanisms of legitimation—such as blockchain-based reporting, the influence of social media, and algorithmic accountability. This study contributes to mapping the conceptual evolution of Legitimacy Theory in a context marked by digital transformation and regulatory intensification, while also identifying promising directions for future research that articulates sustainability, technological innovation, and the construction of legitimacy.