This study investigates the association between gut microbiota and glioblastoma (GBM) using Mendelian randomization (MR). The research team analyzed 211 gut microbiota and GBM genome-wide association study (GWAS) data to determine potential causal relationships. The study employed three MR methods: Inverse Variance Weighted (IVW), MR-Egger, and Weighted Median (WM), along with quality control measures to assess heterogeneity and pleiotropy. The results indicate that nine gut microbiota are associated with GBM risk, with family.Ruminococcaceae showing a protective effect against GBM. After applying the Benjamini-Hochberg correction, family.Ruminococcaceae was identified as significantly associated with a reduced risk of GBM. Other microbiota, such as family.Peptostreptococcaceae and genus.Eubacterium brachy group, were associated with an increased risk of GBM. The study also performed reverse MR to assess the potential reverse causal relationship between GBM and gut microbiota, but no significant association was found. The findings suggest that modulating family.Ruminococcaceae could have potential clinical significance in GBM treatment. The study highlights the importance of the gut microbiota in GBM development and underscores the potential of gut microbiota as therapeutic targets for GBM. The research provides insights into the causal relationship between gut microbiota and GBM, offering potential candidates for further functional studies. However, the study has limitations, including the use of GWAS data from a European population and the limited range of gut microbiota analyzed. Further research is needed to validate these findings and explore the mechanisms underlying the association between gut microbiota and GBM.This study investigates the association between gut microbiota and glioblastoma (GBM) using Mendelian randomization (MR). The research team analyzed 211 gut microbiota and GBM genome-wide association study (GWAS) data to determine potential causal relationships. The study employed three MR methods: Inverse Variance Weighted (IVW), MR-Egger, and Weighted Median (WM), along with quality control measures to assess heterogeneity and pleiotropy. The results indicate that nine gut microbiota are associated with GBM risk, with family.Ruminococcaceae showing a protective effect against GBM. After applying the Benjamini-Hochberg correction, family.Ruminococcaceae was identified as significantly associated with a reduced risk of GBM. Other microbiota, such as family.Peptostreptococcaceae and genus.Eubacterium brachy group, were associated with an increased risk of GBM. The study also performed reverse MR to assess the potential reverse causal relationship between GBM and gut microbiota, but no significant association was found. The findings suggest that modulating family.Ruminococcaceae could have potential clinical significance in GBM treatment. The study highlights the importance of the gut microbiota in GBM development and underscores the potential of gut microbiota as therapeutic targets for GBM. The research provides insights into the causal relationship between gut microbiota and GBM, offering potential candidates for further functional studies. However, the study has limitations, including the use of GWAS data from a European population and the limited range of gut microbiota analyzed. Further research is needed to validate these findings and explore the mechanisms underlying the association between gut microbiota and GBM.