AbstractAlloy selection is a very important problem for various fields. Despite that a series of various studies devoted to this problem exists, reliability of experimental and judgmental information is not taken into account in selection of an optimal alloy. However, reliability of information on alloys characteristics significantly affects the results of choosing an alloy, which satisfies a predefined objective in the best way. In this study, for the first time we consider application of the Z-number theory for optimal alloy selection. The suggested approach is based on an aggregation of Z-number-valued information, Z-number ranking procedures and Z-information processing. The suggested approach is applied for selection of an optimal alloy from the set of alloys created by the authors. This application shows validity, good interpretability and universality of the proposed approach.