A two-sample Mendelian randomization study investigated the causal relationship between gut microbiota and biological aging using the largest available gut microbiota GWAS summary data and biological age acceleration data. The study identified several bacterial genera associated with biological age acceleration, including Streptococcus, Eubacterium (rectale group), Sellimonas, Actinomyces, Butyricimonas, and Lachnospiraceae (FCS020 group). Streptococcus was found to have a causal association with Bioage acceleration, while Eubacterium (rectale group) showed a suggestive causal association. Other genera, such as Lachnospira, were found to have a protective effect on Bioage acceleration. The study also found that certain genera, like Actinomyces and Butyricimonas, were associated with PhenoAge acceleration. Sensitivity analyses using MR-PRESSO, MR-Egger, and other methods confirmed the robustness of these findings. The study highlights the potential role of gut microbiota in biological aging and suggests that modulating gut microbiota could be a strategy for promoting healthy aging. However, further research is needed to validate these findings and explore the mechanisms underlying the causal relationships identified.A two-sample Mendelian randomization study investigated the causal relationship between gut microbiota and biological aging using the largest available gut microbiota GWAS summary data and biological age acceleration data. The study identified several bacterial genera associated with biological age acceleration, including Streptococcus, Eubacterium (rectale group), Sellimonas, Actinomyces, Butyricimonas, and Lachnospiraceae (FCS020 group). Streptococcus was found to have a causal association with Bioage acceleration, while Eubacterium (rectale group) showed a suggestive causal association. Other genera, such as Lachnospira, were found to have a protective effect on Bioage acceleration. The study also found that certain genera, like Actinomyces and Butyricimonas, were associated with PhenoAge acceleration. Sensitivity analyses using MR-PRESSO, MR-Egger, and other methods confirmed the robustness of these findings. The study highlights the potential role of gut microbiota in biological aging and suggests that modulating gut microbiota could be a strategy for promoting healthy aging. However, further research is needed to validate these findings and explore the mechanisms underlying the causal relationships identified.