PERBANDINGAN PELAKSANAAN IMKANUR RUKYAT MABIMS DI MALAYSIA DAN BRUNEI DARUSSALAMNIM.: 22103060072Nadia Ammira binti IndraauthorThe determination of the beginning of the Hijri month is a crucial issue in Islamic astronomy (falak) as it is directly related to the observance of Islamic rituals such as Ramadan fasting, Eid al-Fitr, Eid al-Adha, and the Hajj pilgrimage. In the Southeast Asian context, member states of MABIMS have adopted the Imkan al-Ru’yah criteria as a common guideline to promote the harmonization of the Hijri calendar. Despite employing the same criteria, differences in the determination of the beginning of Hijri months continue to occur in practice among some member countries. This situation indicates that the issue lies not only in the criteria themselves but also in their implementation, institutional mechanisms, moon-sighting verification processes, and geographical factors that influence decision-making. Therefore, this study aims to analyze and compare the implementation of the MABIMS Imkan al-Ru’yah criteria in determining the beginning of the Hijri month in Malaysia and Brunei Darussalam and to examine its application through the perspective of Burhani epistemology. This study is a field research employing a normative-empirical approach. Primary data were obtained through interviews with individuals directly involved in the determination of the beginning of the Hijri month, namely officials from the Falak Division of the Sarawak Mufti Department in Malaysia and officers from the Syariah Judiciary Department and the Survey Department of Brunei Darussalam. Secondary data were collected through documentation, including regulations, crescent moon observation reports, literature on Islamic astronomy, and official MABIMS documents. Data collection techniques consisted of interviews and documentation, while data analysis was conducted using descriptive-analytical and comparative methods. Burhani epistemology was employed as the analytical framework to assess the rationality, empirical observation, and scientific reasoning underlying the implementation of the Imkan al-Ru’yah criteria. The findings reveal that both Malaysia and Brunei Darussalam implement the revised 2021 MABIMS Imkan al-Ru’yah criteria as the basis for determining the beginning of the Hijri month through the integration of astronomical calculations (hisab) and crescent moon observation (ru’yah). However, differences exist in their institutional structures, moon-sighting verification mechanisms, and management of observational data. Analysis based on Burhani epistemology demonstrates that the implementation of the Imkan al-Ru’yah criteria in both countries is founded upon empirical evidence and rational astronomical considerations. Geographical factors, including horizon conditions, atmospheric characteristics, and observation site locations, also influence the visibility of the crescent moon and the decision-making process. Although technical and administrative differences remain, both countries demonstrate a shared commitment to implementing the Imkan al-Ru’yah criteria in a scientifically and religiously accountable manner to support the harmonization of the Hijri calendar within the MABIMS region.297.413 Perbandingan Mazhab2026-06-09UIN SUNAN KALIJAGA YOGYAKARTA;FAKULTAS SYARI’AH DAN HUKUMThesis