The performance and the cost of electrocatalysts play the two most vital roles in the development and application of energy conversion technologies. Single-atom catalysts (SACs) are recently emerging as a new frontier in catalysis science. With maximum atom-utilization efficiency and unique properties, SACs exhibit great potential for enabling reasonable use of metal resources and achieving atomic economy. However, fabricating SACs and maintaining the metal centers as atomically dispersed sites under synthesis and catalysis conditions are challenging. Here, we highlight and summarize recent advances in wet-chemistry synthetic methods for SACs with special emphasis on how to achieve the stabilization of single metal atoms against migration and agglomeration. Moreover, we summarize and discuss the electrochemical applications of SACs with a focus on the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and CO2 reduction reaction (CO2RR). At last, the current issues and the prospects for the development of this field are discussed. Display omitted The development of synthetic strategies plays a fundamental role in advancing catalysis science and practical application of single-atom catalysts (SACs). Owing to the high surface energy of single atoms, achieving the atomic dispersion of mononuclear metal precursors and stabilizing the as-formed single atoms against migration and agglomeration are key aspects in the synthesis of SACs. Several innovative synthetic strategies for SACs are summarized and highlighted through discussion of recent advances in the synthesis of SACs via wet-chemistry approaches. Furthermore, the great potential of SACs in electrochemical applications, with special emphasis on key clean energy conversion reactions including the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and CO2 reduction reaction (CO2RR), are presented and discussed. Further research on single-atom catalysis should focus on understanding the structure-performance relationship and catalytic mechanism at the atomic scale by employing SACs as model systems with the aid of theoretical calculation and in situ characterization technologies to achieve an atomic-economic green catalytic process. Developing single-atom catalysts (SACs) plays a fundamental role in advancing catalysis science and practical application. Owing to high surface energy, fabricating SACs remains a great challenge. In this review, we not only summarize recent advances on wet-chemistry methods and discuss the key points for the synthesis of SACs, but also highlight the potential applications of SACs for clean energy conversion reactions.