Metal sulfide ion-exchangers (MSIEs) represent a new addition to the field of ion exchange materials. This is a growing class of materials that display exceptional selectivity and rapid sorption kinetics for soft or relatively soft metal ions as a result of their soft basic frameworks. Without requiring functionalization, they outperform the most efficient sulfur-functionalized materials. This is the first review focusing on this class of materials; it covers the most important MSIEs, focusing on their synthesis, structural features and ion-exchange chemistry. Furthermore, recent developments in the engineered and composite forms of MSIEs are described. Future research opportunities are also discussed in the hope of inspiring additional scientists to engage in this new area of research on sulfidic ion-exchange materials.