ABSTRAKKulit durian (60-75% bagian durian) mengandung selulosa 55,3%, lignin 19,3% dan abu 6,1%. Kandungan selulosa yang cukup tinggi dalam kulit durian merupakan potensi bioetanol. Tetapi, kandungan lignin dalam kulit durian mengganggu proses pembuatan bioetanol. Lignin bersifat cukup resisten terhadap degradasi kimia dan biologi, sehingga menghambat proses fermentasi. Diperlukan pretreatment proses delignifikasi untuk membantu proses fermentasi. Proses delignifikasi membutuhkan senyawa basa kuat dalam proses pemisahan lignin dari selulosa. Delignifikasi dalam penelitian ini dilakukan dengan aplikasi NaOH 2%, 3%, 4%, 5% dan 6% dan waktu 60, 90 dan 120 menit. Pretreatment delignifikasi diharapkan meningkatkan kadar selulosa dan menurunkan kadar lignin. Kondisi terbaik pretreatment delignifikasi yaitu larutan pemasak NaOH 6%w/v dengan waktu 120 menit yang menghasilkan 83,05%w/w selulosa dan 8,03%w/w lignin. Larutan pemasak NaOH dengan konsentrasi yang tinggi dan waktu delignifikasi yang semakin lama menurunkan kadar lignin dan meningkatkan selulosa. Kata kunci : Delignifikasi, Lignin, Limbah Kulit Durian, NaOH, SelulosaABSTRACTDurian peel (60-75%) contains cellulose 55.3%, lignin 19.3%, and ash 6.1%. Due to its high cellulose content, durian peel can be utilized and processed into bioethanol. However, in the production of bioethanol using durian peel waste as a raw material, lignin interferes the bioethanol production process: lignin. Lignin chemically and biologically resistant to degradation restricting the fermentation process. Therefore, a pretreatment delignification process is required before fermentation. A strong alkaline compound is needed in the delignification process to separate lignin from cellulose. This study uses NaOH as a strong base in the delignification process. The variations used in this study are the concentration of NaOH (2%, 3%, 4%, 5%, and 6%) and time (60, 90, and 120 minutes). Delignification pretreatment affects the cellulose and lignin content produced, with the best delignification pretreatment condition being a 6%w/v NaOH cooking solution for 120 minutes, resulting in a cellulose content of 83.05%w/w and a lignin content of 8.03%w/w. Increase concentration of NaOH as the cooking solution and longer time of the delignification time, increase cellulose obtained and decrease lignin content Keywords : Cellulose, Delignification, Lignin, NaOH, Waste peel of Durian