Circular RNAs (circRNAs) are non-coding RNA molecules with unique properties and diverse functions, increasingly studied in cancer research. They are stable, often tissue-specific, and can act as microRNA (miRNA) sponges, influencing gene regulation. While many circRNAs are conserved and have regulatory roles, their functional relevance in cancer remains largely unexplored. CircRNAs may serve as diagnostic, prognostic, or therapeutic targets in personalized medicine. Their biogenesis involves alternative splicing and is regulated by factors like ADAR, QKI, and DHX9. CircRNAs can function as miRNA sponges, protein sponges, scaffolds, or regulators of splicing and transcription. Some circRNAs, like ciRS-7, have been shown to regulate miR-7 activity, affecting cancer progression. CircRNAs are involved in various cancer hallmarks, including cell cycle regulation, angiogenesis, and metastasis. Deregulated circRNA expression is observed in multiple cancers, such as breast, lung, and ovarian cancer. However, challenges remain in validating circRNA functions and translating findings into clinical applications. Future research should focus on improving circRNA detection methods, understanding their roles in cancer, and exploring their potential as therapeutic targets. CircRNA research is still in its early stages, with a need for standardized reporting and further investigation into their biological functions and clinical relevance.Circular RNAs (circRNAs) are non-coding RNA molecules with unique properties and diverse functions, increasingly studied in cancer research. They are stable, often tissue-specific, and can act as microRNA (miRNA) sponges, influencing gene regulation. While many circRNAs are conserved and have regulatory roles, their functional relevance in cancer remains largely unexplored. CircRNAs may serve as diagnostic, prognostic, or therapeutic targets in personalized medicine. Their biogenesis involves alternative splicing and is regulated by factors like ADAR, QKI, and DHX9. CircRNAs can function as miRNA sponges, protein sponges, scaffolds, or regulators of splicing and transcription. Some circRNAs, like ciRS-7, have been shown to regulate miR-7 activity, affecting cancer progression. CircRNAs are involved in various cancer hallmarks, including cell cycle regulation, angiogenesis, and metastasis. Deregulated circRNA expression is observed in multiple cancers, such as breast, lung, and ovarian cancer. However, challenges remain in validating circRNA functions and translating findings into clinical applications. Future research should focus on improving circRNA detection methods, understanding their roles in cancer, and exploring their potential as therapeutic targets. CircRNA research is still in its early stages, with a need for standardized reporting and further investigation into their biological functions and clinical relevance.