Penelitian ini membahas dampak delimitasi maritim yang belum disepakati terhadap masyarakat pesisir, khususnya nelayan di Tanjung Datu, Kalimantan Barat, Indonesia. Topik ini dipilih karena lautan, sebagai kekayaan berharga bagi negara-negara maritim, sering menjadi pusat ketegangan dan konflik, terutama terkait wilayah delimitasi maritim yang belum disepakati antara negara tetangga. Tujuan penelitian ini adalah mengidentifikasi dampak delimitasi maritim terhadap hak dan mata pencaharian nelayan di Tanjung Datu serta menyoroti ancaman terhadap tradisi, mata pencaharian, dan ekonomi masyarakat pesisir di wilayah ini akibat ketidakjelasan batas maritim antara Indonesia dan Malaysia. Metode penelitian yang digunakan menggabungkan pendekatan hukum normatif dan empiris. Pendekatan hukum normatif menganalisis kerangka hukum internasional dan nasional terkait delimitasi maritim, sementara pendekatan hukum empiris melibatkan studi kasus di Tanjung Datu. Data diperoleh melalui wawancara, observasi, dan analisis dokumen, dengan fokus pada dampak ekonomi, sosial, dan budaya. Hasil penelitian menunjukkan bahwa dampak utama delimitasi maritim adalah pada aspek ekonomi, dengan perubahan hak akses dan ketidakpastian ekonomi; dampak sosial berupa ancaman terhadap keamanan masyarakat pesisir; serta dampak budaya terkait kekhawatiran terhadap pelestarian budaya dan tradisi. Konflik antara Indonesia dan Malaysia juga menimbulkan ketidakpastian hukum wilayah perairan tangkap ikan nelayan. Urgensi penyelesaian delimitasi maritim yang adil dan berkelanjutan untuk mengakomodir kebutuhan masyarakat pesisir, menjaga keberlanjutan warisan budaya lokal, serta menciptakan kondisi stabil dan sejahtera bagi komunitas pesisir yang bergantung pada sumber daya laut. Title: Impact of Maritime Delimitation on Coastal Communities at the Indonesia-Malaysia Border in West Kalimantan This study examines the impact of unresolved maritime delimitation on coastal communities, particularly fishermen in Tanjung Datu, West Kalimantan, Indonesia. The topic was chosen because oceans, as valuable assets for maritime countries, often become centers of tension and conflict, especially regarding unresolved maritime boundaries between neighboring countries. The purpose of this research is to identify the impact of maritime delimitation on the rights and livelihoods of fishermen in Tanjung Datu and to highlight threats to the traditions, livelihoods, and economies of coastal communities in this region due to the unclear maritime boundaries between Indonesia and Malaysia. The research methodology combines normative legal and empirical approaches. The normative legal approach analyzes the international and national legal frameworks related to maritime delimitation, while the empirical legal approach involves a case study in Tanjung Datu. Data were collected through interviews, observations, and document analysis, focusing on economic, social, and cultural impacts. The research findings indicate that the primary impact of maritime delimitation is economic, with changes in access rights and economic uncertainty; the social impact includes threats to the security of coastal communities; and the cultural impact relates to concerns about preserving cultural heritage and traditions. The conflict between Indonesia and Malaysia also creates legal uncertainty regarding the fishing waters of fishermen. There is an urgency to resolve maritime delimitation fairly and sustainably to accommodate the needs of coastal communities, preserve their cultural heritage, and create stable and prosperous conditions for coastal communities that rely on marine resources.