ABSTRAK Penelitian ini bertujuan untuk mengetahui keanekaragaman jenis ikan di Sungai Lae Cinendang, Kabupaten Aceh Singkil, Provinsi Aceh. Sampel diambil secara purposive sampling dari empat stasiun penelitian dengan rona lingkungan berbeda, yaitu hutan, perkampungan, industri, dan perkebunan. Hasil identifikasi menunjukkan bahwa ikan yang ada di Sungai Lae Cinendang meliputi Famili Cyprinidae yaitu Rasbora sp., Anematichthys apogon, dan Osteochilus vittatus, dan ikan Famili Bagridae yaitu Leiocassis micropogon, Mystus micracanthus, dan Hemibagrus caveatus. Indeks keanekaragaman keempat stasiun tergolong kriteria sedang dengan kisaran nilai 1,04-1,47, sedangkan indeks kesamaan jenis ikan tergolong kriteria mirip dengan kisaran nilai 66-88%. Adapun kondisi fisika-kimia air Sungai Lae Cinendang masih tergolong optimum bagi keberlangsungan hidup ikan. Kata kunci: Lae Cinendang, keanekaragaman jenis, ikan ABSTRACT The research to observe of the diversity of fish species on Lae Cinendang river, Aceh Singkil Regency, Aceh Province. The samples were taken with purposive sampling from four research stations with different environment condition, that is forested, settlements, industry, and plantations. Results showed that the fish species on Lae Cinendang river covered Family Cyprinidae which were Rasbora sp., Anematichthys apogon, and Osteochilus vittatus, and Famili Bagridae which were Leiocassis micropogon, Mystus micracanthus, and Hemibagrus caveatus. Diversity index was showed that fish species from four station including criteria of moderate with the range 1.04-1.47, therefore similarity index of fish species from four research station including criteria of similar with the range 66-88%. As for the physical-chemical conditions the waters of Lae Cinendang still considered optimum for the survival of fish . Keywords: Lae Cinendang, diversity of species, fish