The selection of suitable landfill locations for municipal solid waste has become a top priority, especially in developed countries as a result of rapid population growth, unplanned urbanisation, increasing waste production and the limited area available. However, determining the location of landfill sites is a complex decision-making problem for municipalities and depends on social, environmental, technical and economic factors and regulations. In this study, we combined a geographic information system (GIS), multi-criteria decision-analysis techniques and fuzzy logic to determine the best location for landfill sites in Adana, Turkey, in four steps. Firstly, the threshold values and the coefficient weights of 15 criteria, grouped into environmental and socio-economic factors, were determined by a literature review and expert opinion to select suitable landfill locations. Secondly, selection criteria were standardised using fuzzy logic. Thirdly, we assessed the criteria weights based on their effectiveness on the selection of potential landfill sites using the Simos method. According to the weight coefficients, environmental factors are more important than socio-economic factors. Final maps for each criterion were calculated and overlaid by a GIS. As a result, the final suitability results were divided into four discrete categories: very high, high, moderate and low suitability areas, representing 1%, 76%, 17% and 6% of the location options, respectively. Finally, four different alternative areas were identified as being very highly suitable for landfill locations, which were evaluated in detail using a strengths, weaknesses, opportunities and threats analysis. Three key aspects affect the final decision of a landfill site, in decreasing order of importance: environmental protection, minimising the negative impact on urban life quality and economic issues. Consequently, these results can guide decision-makers (ministries, municipalities, planners, etc.) during the selection of suitable landfill sites in both national and international studies.