This article examines the digital marketization of nikah siri (unregistered marriage) in Indonesia within the framework of legal pluralism and its implications for marriage governance. The growing promotion of nikah siri services through social media reflects a structural shift in which unregistered marriage practices are transformed into a digital and commercialized marketplace, generating significant legal and regulatory concerns. Indonesian marriage law, particularly Law No. 1 of 1974 as amended by Law No. 16 of 2019, Government Regulation No. 9 of 1975, and Ministerial Regulation (PMA) No. 30 of 2024, requires official marriage registration, yet unregistered practices persist within overlapping systems of state law, Islamic law, and customary norms. The study employs a socio-legal approach combined with doctrinal legal analysis, using secondary legal sources, regulatory documents, and publicly available digital data. The findings show that platform-based promotion creates regulatory grey zones that weaken state enforcement and expand informal marriage markets involving intermediaries, religious actors, and service brokers. The novelty of this study lies in conceptualizing nikah siri as a digitally mediated, market-driven phenomenon shaped by the interaction of legal pluralism and platform economy dynamics. The study contributes to socio-legal scholarship by highlighting structural limitations in Indonesia’s marriage governance, particularly the gap between legal norms and enforcement capacity. Strengthening regulation requires legal reform and institutional reinforcement of marriage registration alongside adaptive digital governance strategies. The study is limited to doctrinal and socio-legal analysis based on secondary and publicly available digital sources, without fieldwork or interviews, suggesting avenues for future empirical research.