This chapter introduces feasibility studies for mineral projects at various stages, focusing on scoping studies, prefeasibility studies, and feasibility studies, along with their data requirements. It delineates the distinct objectives and characteristics of each phase, including typical durations, costs, and accuracies. Scoping studies are described as preliminary assessments that provide an initial evaluation of a mineral project’s potential. Prefeasibility studies offer a more in-depth technical and economic analysis of multiple project options. Full feasibility studies present comprehensive evaluations of the most favorable option identified in the prefeasibility study, aiming to eliminate uncertainties and enhance the accuracy of estimates, which serve as the foundation for decision-making and securing project financing. The chapter also addresses the outcomes and applications of feasibility studies, emphasizing the importance of thorough risk identification and the development of effective mitigation strategies to enhance project robustness. Furthermore, the chapter introduces methods for estimating mining project costs during feasibility studies, including production rate-based empirical methods such as O’Hara models and cost indexing methods.