PERKAWINAN TIDAK TERCATAT OLEH SUKU SAMIN DI DUSUN JEPANG DESA MARGOMULYO KECAMATAN MARGOMULYO KABUPATEN BOJONEGORO (STUDI KOMPARATIF HUKUM POSITIF, HUKUM ADAT DAN MASLAHAH MURSALAH )NIM.: 22103060057Evie Eka NurainiauthorUnregistered marriages among the Samin people in Japan Hamlet, Margomulyo Village, Bojonegoro, demonstrate a new dynamic in the practice of marriage law in Indonesia. The rejection of administrative registration in state institutions is based on the firm adherence to ancestral teachings (Saminism), which believe that marriage is a sacred bond and is sufficiently witnessed by God and the Sedulur Sikep community through the Pasuwitan traditional ritual. This practice raises legal issues related to the lack of formal legality in the eyes of the state, which directly impacts the fulfillment of the civil rights of wives and children. Based on this phenomenon, this study formulates two questions: how the legal status of unregistered marriages among the Samin people compares from the perspectives of positive law and customary law, and how the Maṣlaḥah Mursalah theory analyzes the practice of unregistered marriages. The aim is to analyze the legal status of Samin marriages comparatively and to dissect their benefits and drawbacks using the framework of Imam Al-Ghazali's thought. This research is a field research with a normative-empirical approach. Primary data was obtained through in-depth interviews with traditional leaders of the Samin Tribe and residents who participated in traditional Samin marriages. Secondary data was collected from laws and regulations (Law Number 1 of 1974), legal literature, books on Islamic jurisprudence (ushul fiqh), and relevant scientific works. The analysis technique used is descriptive-analytical and comparative, namely describing marriage practices according to positive law provisions and Samin Customary Law using the theory of Maṣlaḥah Mursalah to find a solution for the benefit of both. The results of the study indicate that there are fundamental differences regarding the validity of marriage between the two legal systems. From a positive legal perspective, Samin marriages are considered to have no formal legal force because they are not registered with the KUA (Religious Affairs Office) or the Civil Registry Office as required by Article 2 of the Marriage Law. Conversely, in Samin customary law, a marriage is declared fully valid after fulfilling a series of Pasuwitan rituals (starting from the Jawab, Paseksen, to Tasyakuran stages) based on social-community recognition. Meanwhile, based on the analysis of Imam Al-Ghazali's Maṣlaḥah Mursalah theory, Samin customary marriages on the one hand contain benefits in maintaining spiritual values (ḥifẓ al-dīn), harmony (ḥifẓ al-nafs), and a lifelong commitment to fidelity (siji kanggo sak lawase). However, on the other hand, the lack of state registration poses significant challenges to the protection of children's lineage (ḥifẓ al-nasl) and economic/inheritance rights (ḥifẓ al-māl). Therefore, these two legal systems need to be bridged through the adaptation of marriage registration as a means of legal protection (benefit for wives and children) without eliminating the values of local Samin customary wisdom.340.2 Hukum Perbandingan2026-06-02UIN SUNAN KALIJAGA YOGYAKARTA;FAKULTAS SYARIAH DAN HUKUMThesis