Abstract Energy storage and transportation technologies play an important role in space exploration missions. Regenerative fuel cells are among the most promising sustainable energy power sources. Compared to secondary batteries, regenerative fuel cells possess unique advantages, including high power density, high specific energy density, light-weight, low-cost, high-efficiency, long-life, and zero environmental impact. More importantly, an regenerative fuel cell is an electrochemical device that can collect and store solar energy during the daytime and release it gradually whenever is needed, making energy available 24/7. Therefore, the development of high-performance regenerative fuel cells in the aerospace sector is becoming more and more important. Herein, in this review, various types of fuel cells are briefly introduced, followed by a detailed discussion and comparison between different unitized regenerative fuel cells. Electrocatalysts and membranes are two of the essential components in the unitized regenerative fuel cells that play a key role in enhancing the system's efficiency. Thus, recent progress and challenges on bifunctional hydrogen and oxygen electrodes are systematically summarized and discussed, respectively. More importantly, the progress and challenges of proton and anion electrolyte membranes are discussed. Further, power performance and durability are two important measures for the application of regenerative fuel cells in space energy systems. Therefore, the current progress of fuel cells in power performance and durability are summarized and discussed. In the end, the key issues and future perspectives of unitized regenerative fuel cells toward space energy storage and transportation are presented.