Abstract: This work reviews technologies that can be used to develop low-temperature solid oxide cells (LT-SOCs) and can be applied in fuel cells and electrolyzers operating at temperatures below 500°C, thus providing a more cost-effective alternative than conventional high-temperature SOCs. Two routes showing potential to reduce the operating temperature of SOCs to below 500°C are discussed. The first route is the principal way to enhance cell performance, namely, structure optimization. This technique includes the reduction of electrolyte thickness to the nanometer scale and the exploration of electrode structure with low polarization resistance. The other route is the development of novel proton-conducting electrolyte materials, which is in the frontier of SOCs study. The fundamentals of proton conduction and the design principles of commonly used electrolyte materials are briefly explained. The most widely studied electrolyte materials for LT-SOCs, namely, perovskite-type BaCeO₃- and BaZrO₃-based oxides, and the effect of doping on the physical–chemical properties of these oxide materials are summarized.