Circular RNAs (circRNAs) are a recently discovered type of endogenous RNA molecules that are formed through the back-splicing process of exons in precursor messenger RNAs (pre-mRNAs), resulting in a unique covalently closed circular structure. CircRNAs are just beginning to be acknowledged for their roles as microRNA sponges and protein scaffolds, their ability to regulate transcription and splicing, and their occasional use as templates for polypeptide synthesis. However, the exploration of their functions is still in its early stages. circRNAs have essential functions in a wide range of different cellular functions. The abnormal presence of circRNAs in tumors contributes to continuous cell proliferation and growth, enhances invasion capabilities, and evades the process of cell aging and death. This indicates the possibility of using them as markers and targets for treatment in a clinical setting. This article provides a thorough examination of current advancements in the study of circular RNAs (circRNAs) in cancer, focusing particularly on their molecular mechanisms and potential impact in a clinical setting.