Proses seleksi peserta Olimpiade Sains Nasional (OSN) di SMAN 1 Ciwaru masih memerlukan waktu lama sehingga membutuhkan waktu lama dan berpotensi kurang objektif. Penelitian ini bertujuan mengembangkan Sistem Pendukung Keputusan menggunakan metode PROMETHEE untuk meningkatkan akurasi dan efisiensi proses seleksi. Lima kriteria digunakan dalam perhitungan, yaitu nilai rata-rata rapor, nilai rata-rata mata pelajaran cabang OSN, nilai rata-rata tes, absensi bimbingan sebagai kriteria cost, dan nilai simulasi akhir tes. Sistem dikembangkan dengan metode Waterfall menggunakan framework Laravel dan database MySQL. Metode PROMETHEE diterapkan untuk menghitung nilai leaving flow, entering flow, dan net flow pada empat cabang OSN: Matematika, Fisika, Kimia, dan Biologi. Berdasarkan hasil perangkingan, sistem menghasilkan peserta terbaik dengan nilai net flow tertinggi masing-masing sebesar 0,9500; 0,9632; 0,8471; dan 0,8000. Hasil ini menunjukkan bahwa metode PROMETHEE mampu memberikan rekomendasi peserta yang objektif, transparan, dan konsisten sesuai kriteria yang ditetapkan. Secara keseluruhan, sistem yang dibangun dapat meningkatkan efektivitas seleksi peserta OSN di SMAN 1 Ciwaru.
The selection process for National Science Olympiad (OSN) participants at SMAN 1 Ciwaru still requires a long time, making it inefficient and potentially less objective. This study aims to develop a Decision Support System using the PROMETHEE method to improve the accuracy and efficiency of the selection process. Five criteria were used in the evaluation, namely average report card scores, average scores of OSN-related subjects, average test scores, attendance in OSN training sessions as a cost criterion, and final test simulation scores. The system was developed using the Waterfall method with the Laravel framework and MySQL database. The PROMETHEE method was applied to calculate leaving flow, entering flow, and net flow for four OSN branches: Mathematics, Physics, Chemistry, and Biology. Based on the ranking results, the system produced the best participants with the highest net flow values of 0.9500, 0.9632, 0.8471, and 0.8000, respectively. These results demonstrate that PROMETHEE effectively provides objective, transparent, and consistent participant recommendations according to the defined criteria. Overall, the developed system improves the effectiveness of the OSN participant selection process at SMAN 1 Ciwaru.