Ion-exchangeable, transparent spinel glass-ceramics are presented and discussed here for the first time. To retain transparency with increasing crystallinity, spinel glass-ceramics must have uniform crystallization of small (similar to 9 nm) crystallites, not large spherulitic structures comprised of small crystallites. To obtain such a uniform microstructure, the amount of total nucleating agents (ZrO2 + TiO2) in the precursor glass composition must be greater than 5 mol%. With small changes in composition and significant differences in microstructure, the demarcation between transparent and opaque glass-ceramics is distinct as is the decrease in K diffusivity during ion-exchange from the transparent (14.7 microns(2)/h) to the opaque (11.2 microns(2)/h) compositions. Understanding how to retain transparency during ceramming and increase diffusivity during chemical strengthening is critical in designing materials for many real-world applications. Ion-exchangeable, transparent spinel glass-ceramics are presented and discussed here for the first time. To retain transparency with increasing crystallinity, spinel glass-ceramics must have uniform crystallization of small (similar to 9 nm) crystallites, not large spherulitic structures comprised of small crystallites. To obtain such a uniform microstructure, the amount of total nucleating agents (ZrO2 + TiO2) in the precursor glass composition must be greater than 5 mol%. With small changes in composition and significant differences in microstructure, the demarcation between transparent and opaque glass-ceramics is distinct as is the decrease in K diffusivity during ion-exchange from the transparent (14.7 microns(2)/h) to the opaque (11.2 microns(2)/h) compositions. Understanding how to retain transparency during ceramming and increase diffusivity during chemical strengthening is critical in designing materials for many real-world applications.