Circular RNAs (circRNAs),a group of highly conserved small RNAs,are characterized by a closed circular structure from precursor linear RNA through reverse splicing.They are powerful regulators of the physiological and pathological processes in organisms at different development stages.Zebrafish can be used for the high-throughput drug screening with low cost.Thus,the circRNAs associated with development and inflammation can be mined from zebrafish.Recently,a variety of circRNAs in zebrafish have been identified and characterized.Studies have proved that circRNAs play a vital role in the development and inflammation of zebrafish.The paper summarizes the classification,characteristics,and biological functions of circRNAs,and reviews the research progress in zebrafish's circRNAs.