One of the most basic aspects of the pluralism of the Indonesian nation is the existence of a plurality of religions embraced by its population. Guarantees for the existence of religion and belief have been regulated by the State in Article 29 paragraph (1) and paragraph (2) of the 1945 Constitution. The diversity of religions and beliefs in Indonesia can have implications for the occurrence of marriages between adherents of religions and beliefs. Law Number 1 of 1974 concerning Marriage jo. Government Regulation no. 9 of 1975. Article 2 paragraph (1) of Law Number 1 of 1974 concerning Marriage clearly stipulates that "Marriage is legal, if it is carried out according to the laws of each religion and belief. This research is classified as normative legal research. Research Results Interfaith marriage is something that cannot be justified based on the Marriage Law and the Compilation of Islamic Law, with the consideration that the issuance of these rules is to avoid the occurrence of greater harm/loss (mafsadat) in addition to the good/gain (maslahat) that arise. Articles 40 (c) and 44 of the Compilation of Islamic Law (KHI) clearly prohibit the marriage of people who are Muslim to people who are not Muslim as also stated in the 1945 Constitution article 20 paragraph 2, that there is no marriage outside the law of each his religion and beliefs.