Nanozymes with intrinsic enzyme-like properties have attracted significant interest owing to their capability to address the limitations of traditional enzymes such as fragility,high cost and difficult mass production.However,the currently reported nanozymes are generally less active than natural enzymes.In recent years,with the rapid development of nanoscience and nanotechnology,single-atom nanozymes(SAzymes)with well-defined elec-tronic and geometric structures have shown a promise to serve as direct surrogates of traditional enzymes by mimicking the highly evolved catalytic center of natural enzymes.In this review,we will introduce the enzymatic characteristics and recent advances of SAzymes,and summarize their sig-nificant applications from in vitro detection to in vivo monitoring and therapy.