An unregistered marriage “perkawinan sirri” is a marriage solemnized in accordance with religious tenets but carries the potential for various legal consequences—particularly for women—such as difficulties in securing legal certainty and the fulfillment of civil rights. Given this context, this study aims to analyze (1) the legal consequences of unregistered marriages for women and (2) the forms of legal protection available to women in such marriages within the jurisdiction of the Pandeglang Religious Court. The study employs an empirical-juridical research method, utilizing statutory, conceptual, and legal effectiveness approaches. Data were gathered through interviews with judges and court clerks at the Pandeglang Religious Court, supplemented by a literature review, and were analyzed qualitatively. The findings indicate that unregistered marriages result in a lack of legal certainty regarding marital status, thereby hindering women from accessing civil rights such as entitlement to maintenance “nafkah”, claims to marital assets, and the ability to prove their marital status. Legal protection for women is facilitated through the “isbat” (marriage ratification) mechanism at the Religious Court, serving as a means to obtain state recognition for a marriage that was originally solemnized solely under religious law. The study concludes that unregistered marriages disadvantage women due to the absence of official marriage registration. Consequently, “isbat nikah” (marriage ratification) serves as a form of legal protection that establishes certainty regarding marital status and safeguards the rights of both women and children.