Abstract: Intratumoral bacteria are a group of bacteria that exist within tumors and make up the tumor microenvironment. They play a significant role in tumorigenesis and progression, as well as in influencing the response of tumors to chemotherapy and immunotherapy through various mechanisms. This article primarily discusses the sources and mechanisms of action of intratumoral bacteria, with a specific focus on their composition and functions in the digestive system. Further-more, it explores the potential application of intratumoral bacteria in anti‑tumor therapy, aiming to provide valuable references for future clinical use.