Abstrak Limbah cangkang rajungan yang mencapai 40-60% dari total bobot rajungan selama ini hanya dibuang ke lingkungan sehingga menimbulkan pencemaran di daerah pesisir. Kegiatan pengabdian masyarakat ini bertujuan memberikan edukasi dan pelatihan kepada kelompok nelayan "Mappedeceng" di Desa Lasitae, Kecamatan Tanete Rilau, Kabupaten Barru tentang pemanfaatan limbah cangkang rajungan menjadi kitosan sebagai pengawet alami. Metode pelaksanaan terdiri dari tiga tahapan yaitu persiapan, pelaksanaan (penyuluhan, pelatihan teknologi pengolahan, dan praktik langsung), serta evaluasi melalui pre-post test. Kegiatan dilaksanakan pada 9 Agustus 2025 dengan melibatkan 40 peserta. Hasil evaluasi menunjukkan peningkatan pengetahuan peserta sebesar 38,75% berdasarkan perbandingan skor pre-test (rata-rata 10,575) dan post-test (rata-rata 18,325). Kegiatan praktik pembuatan pengawet alami menunjukkan antusiasme tinggi dari peserta, dengan mayoritas merasa percaya diri menerapkan teknologi ini di rumah. Kitosan yang dihasilkan terbukti dapat memperpanjang masa simpan produk perikanan hingga 2-3 kali lipat dan memiliki nilai ekonomi tinggi sekitar Rp 75.000-100.000 per kilogram. Program ini berhasil meningkatkan kesadaran nelayan tentang pentingnya ekonomi sirkular dalam perikanan dan memberikan solusi berkelanjutan untuk mengatasi masalah limbah cangkang rajungan sekaligus menciptakan peluang ekonomi baru bagi masyarakat pesisir. Kata kunci: limbah cangkang rajungan; kitosan; pengawet alami; pemberdayaan nelayan; teknologi pengolahan limbah. Abstract Crab shell waste, which accounts for 40-60% of the total weight of crabs, is often dumped into the environment, causing pollution in coastal areas. This community service activity aims to provide education and training to the "Mappedeceng" fishing group in Lasitae Village, Tanete Rilau District, Barru Regency, on the utilization of crab shell waste into chitosan as a natural preservative. The implementation method consists of three stages: preparation, implementation (counseling, processing technology training, and direct practice), and evaluation through a pre-post test. The activity was carried out on August 9, 2025, involving 40 participants. The evaluation results showed an increase in participant knowledge of 38.75% based on a comparison of pre-test scores (average 10.575) and post-test (average 18.325). The practical activity of making natural preservatives showed high enthusiasm from the participants, with the majority feeling confident in applying this technology at home. The resulting chitosan has been proven to extend the shelf life of fishery products by two to three times and has a high economic value of around IDR 75,000-100,000 per kilogram. This program has successfully raised awareness among fishermen about the importance of a circular economy in fisheries and provided a sustainable solution to address the problem of crab shell waste while creating new economic opportunities for coastal communities. Keywords: crab shell waste; chitosan; natural preservative; fishermen empowerment; waste processing technology.