Solid-state electrolytes and solid-state batteries have recently garnered significant interest to enable unprecedented performance and safety.  While in theory, the performance of solid-state batteries is appealing, in practice numerous manufacturing and cell design challenges are expected owing to the brittle nature of ceramic-based solid electrolytes.  To address these challenges, the mechanical properties of solid electrolytes must be characterized.  The purpose of this work is to characterize the salient properties of promising oxide and sulfide solid electrolytes to facilitate their transition into the manufacturing and testing of solid-state battery prototypes.  Mechanical properties such as the elastic and shear moduli, Poisson’s ratio, fracture toughness, and hardness are presented and their implications discussed.  Additionally, a novel approach to conduct in situ, non-invasive, non-destructive mechanical characterization during and after cycling solid-state prototype cells will be presented.