<p>This study investigates the efficiency of methanesulfonic acid (MSA) as an alternative, environmentally benign leaching agent for extracting metals from municipal solid incineration fly ash (MSWI FA). A series of experiments were conducted to evaluate the effects of key leaching parameters, including ash type, solid-to-liquid ratio, MSA concentration and temperature, on the leachability of metals. MSA combined with 1 vol.% H₂O₂ achieved 96.47 ± 4.3%, 89.52 ± 4.3%, and 45.89 ± 5.1% for Cu, Zn, and Pb, respectively. Pb extraction was significantly enhanced by elevated temperatures and higher acid concentrations. Leaching efficiencies for economically valuable elements such as Cu and Zn remained consistently high across all ash types, indicating their broad solubility. In contrast, the extraction of elements like Pb, Ni, and Cr showed greater variability depending on the ash type, likely due to differences in metal speciation and phase associations. The conductivity of MSA solutions ranged from 0.25 to 0.34 S/cm, indicating suitability for electrowinning applications with minimal pre-treatment. Overall, the results demonstrate that MSA is an effective and competitive leaching agent for the recovery of Cu, Zn, and Pb from MSWI FA, offering performance and cost advantages comparable to other bulk organic acids.</p> Graphical Abstract <p></p>