<p>Even with substantial research on the recycling of valuable materials and energy recovery from waste to mitigate landfill challenges, landfilling continues to be a fundamental aspect of solid waste management. The selection of landfill sites is a critical process that requires careful consideration due to potential threats to the environment and human health. The selection of a suitable site for landfills involves various criteria and constitutes a complex process. Multi-Criteria Decision-Making (MCDM) methods enhance the clarity and suitability of the decision-making process. Each MCDM method possesses distinct benefits, constraints, and applicability that can influence the final outcome. In this paper, a new hybrid framework that combines MCDM methods to improve landfill siting processes is introduced. The framework integrates the Full Consistency Method (FUCOM) with Quintic Fuzzy Sets (QuFS), referred to as QuFS–FUCOM, to prioritize evaluation criteria for landfill sites, addressing uncertainty and ensuring consistency. The Complex Proportional Assessment (COPRAS) method is utilized for ranking landfill sites. The evaluation of five sites based on seven criteria indicated that the Number of Affected People (NAP) is the most important criterion, while Environmental Time (ET) and Distance to Non-Urban Areas (DNUA) are the least important. A₃, which includes two locations, S₃ (East) and S₄ (West), in southwestern Colombia, was identified as the most suitable alternative, whereas A₁, representing S₁ (North) was considered the least suitable. The findings demonstrate the effectiveness of the proposed framework, as evidenced by sensitivity and correlation analysis, which underscores its capacity to produce accurate and robust results.</p>