Carbonized lignin was investigated as a low-cost, sustainable adsorbent for azithromycin removal from aqueous solutions and compared with commercial activated carbon. Both adsorbents were characterized using Brunauer–Emmett–Teller (BET) surface area analysis and Fourier-transform infrared (FTIR) spectroscopy. The BET surface areas were 632 m²/g for carbonized lignin and 707 m²/g for activated carbon. Batch adsorption experiments were designed using the Taguchi method to evaluate the effects of pH, adsorbent dosage, and temperature. The optimum conditions for both adsorbents were pH 3, 60 °C, and an adsorbent dosage of 1.5 g/L. Under these conditions, azithromycin removal efficiencies reached 89.5% and 93.02% for carbonized lignin and activated carbon, respectively. Despite its lower surface area, carbonized lignin exhibited adsorption performance comparable to activated carbon, demonstrating its potential as a cost-effective and environmentally sustainable adsorbent for antibiotic-contaminated water treatment.