River borderlands are areas that play a crucial role in preserving ecosystems, preventing natural disasters such as floods, and supporting environmental sustainability. The management of river borderlands needs to be firmly regulated to ensure legal certainty and the protection of public interests. This study aims to examine the regulation of river borderland management from the perspectives of civil law and Islamic law. The method used is a normative juridical approach, with analysis of legislation, legal literature, and principles of Islamic law. In civil law, river borderlands are classified as areas of public interest where construction is restricted to preserve the river's function. Meanwhile, in Islamic law, the principles of maslahah public benefit and the prohibition of actions that cause harm mudarat serve as the main foundations for regulating the use of river borderlands. Islamic law also emphasizes the collective responsibility of the community to protect natural resources as a trust amanah from Allah. The results of the study indicate that both civil law and Islamic law share common ground in prohibiting the use of river borderlands in ways that harm the environment and society. Therefore, harmonizing positive law with Islamic values is essential to establish a just, sustainable, and environmentally conscious river borderland management system.