© 2021 Elsevier LtdParking is one of the biggest challenges faced by megacities experiencing rapid growth. With more than 15 million population and approximately 3 million passenger cars, Istanbul is a megacity having a considerable parking problem. Sustainable planning of the parking lots in the city requires smarter spatial decision making approaches to use limited land resources efficiently. In order to determine the optimum locations for parking supply in the case of four districts of Istanbul, a GIS-based fuzzy analytical hierarchy process (AHP) approach is employed. In this context, the relevant criteria are identified and collected under three main categories: (1) land use, (2) finance and (3) transportation. Raster grid layers are created in GIS for those criteria through spatial data processing and analysis techniques. Those layers are then combined after being weighted with the fuzzy AHP approach. Thus, the scores of all grid cells in the study area are obtained and then transferred to the land parcels to rank them by their suitability. Besides, the parcels are also evaluated with respect to shape and area. Finally, those assigned to the highest ranking category as well as having proper shape and area are recognized as the feasible parcels for parking lot generation and prioritized according to those factors. The findings showed that the GIS-based fuzzy AHP approach applied in this study enabled multi-criteria investigation of each location (i.e. grid cell) in the study area based on highly detailed spatial data and could therefore be used to determine the feasible parcels for parking lot generation. Among the main criteria, transportation had the greatest weight while finance had the least weight. According to the case study, the need for parking and the number of feasible parcels are greater in Uskudar than the other three districts.