This study investigates the causal relationship between gut microbiota and biological aging using a two-sample Mendelian randomization (MR) approach. The study utilized the largest available gut microbiota genome-wide association study (GWAS) summary data from the MiBioGen consortium and GWAS data on biological age acceleration. The main findings include: 1. **Streptococcus**: Causally associated with biological age acceleration (Bioage acceleration) (IVW, β = 0.16, p = 0.0001). 2. **Eubacterium (rectale group)**: Suggestive of causal association with Bioage acceleration (IVW, β = 0.20, p = 0.0190). 3. **Sellimonas**: Suggestive of causal association with Bioage acceleration (IVW, β = 0.06, p = 0.019). 4. **Lachnospira**: Suggestive of causal association with Bioage acceleration (IVW, β = −0.18, p = 0.01), with the latter being protective. 5. **Actinomyces**: Suggestive of causal association with Phenotype Age acceleration (Phenoage acceleration) (IVW, β = 0.26, p = 0.0083). 6. **Butyricimonas**: Suggestive of causal association with Phenoage acceleration (IVW, β = 0.21, p = 0.0184). 7. **Lachnospiraceae (FC5020 group)**: Suggestive of causal association with Phenoage acceleration (IVW, β = 0.24, p = 0.0194). The study also conducted sensitivity analyses using MR-PRESSO, MR-Egger regression, Cochran Q test, and reverse MR analysis to validate the results. The findings suggest that *Streptococcus* is causally associated with biological age acceleration, while other gut microbiota show suggestive causal effects on aging acceleration or deceleration. Further randomized controlled trials are needed to confirm these findings and explore the mechanisms underlying the causal relationship between gut microbiota and biological aging.This study investigates the causal relationship between gut microbiota and biological aging using a two-sample Mendelian randomization (MR) approach. The study utilized the largest available gut microbiota genome-wide association study (GWAS) summary data from the MiBioGen consortium and GWAS data on biological age acceleration. The main findings include: 1. **Streptococcus**: Causally associated with biological age acceleration (Bioage acceleration) (IVW, β = 0.16, p = 0.0001). 2. **Eubacterium (rectale group)**: Suggestive of causal association with Bioage acceleration (IVW, β = 0.20, p = 0.0190). 3. **Sellimonas**: Suggestive of causal association with Bioage acceleration (IVW, β = 0.06, p = 0.019). 4. **Lachnospira**: Suggestive of causal association with Bioage acceleration (IVW, β = −0.18, p = 0.01), with the latter being protective. 5. **Actinomyces**: Suggestive of causal association with Phenotype Age acceleration (Phenoage acceleration) (IVW, β = 0.26, p = 0.0083). 6. **Butyricimonas**: Suggestive of causal association with Phenoage acceleration (IVW, β = 0.21, p = 0.0184). 7. **Lachnospiraceae (FC5020 group)**: Suggestive of causal association with Phenoage acceleration (IVW, β = 0.24, p = 0.0194). The study also conducted sensitivity analyses using MR-PRESSO, MR-Egger regression, Cochran Q test, and reverse MR analysis to validate the results. The findings suggest that *Streptococcus* is causally associated with biological age acceleration, while other gut microbiota show suggestive causal effects on aging acceleration or deceleration. Further randomized controlled trials are needed to confirm these findings and explore the mechanisms underlying the causal relationship between gut microbiota and biological aging.