The development of solid electrolytes with the combination of high ionic conductivity, electrochemical stability, and resistance to Li dendrites continues to be a challenge. A promising approach is to create inorganic–organic composites, where multiple components provide the needed properties, but the high sintering temperature of materials such as ceramics precludes close integration or co-sintering. Here, new ceramic–salt composite electrolytes that are cold sintered at 130 °C are demonstrated. As a model system, composites of Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) or Li 1+x+y Al x Ti 2−x Si y P 3−y O 12 (LATP) with bis(trifluoromethanesulfonyl)imide (LiTFSI) salts are cold sintered. The resulting LAGP–LiTFSI and LATP–LiTFSI composites exhibit high relative densities of about 90% and ionic conductivities in excess of 10 −4 S cm −1 at 20 °C, which are comparable with the values obtained from LAGP and LATP sintered above 800 °C. It is also demonstrated that cold sintered LAGP–LiTFSI is electrochemically stable in Li symmetric cells over 1800 h at 0.2 mAh cm −2 . Cold sintering provides a new approach for bridging the gap in processing temperatures of different materials, thereby enabling high-performance composites for electrochemical systems.