BACKGROUND: Observational studies suggest that gut microbiome (GM) may contribute to acute anterior uveitis (AAU) development, but causality remains unclear. This study was conducted to test whether specific GM taxa were causally associated with AAU. METHODS: The GM data were obtained from the DMP, which included 7738 individuals' faecal samples and an analysis of host genotype-taxa abundance associations. The AAU data were derived from the FinnGen Consortium (8624 cases and 473,095 controls). We primarily employed the inverse-variance weighted method, complemented by supplementary sensitivity analyses. RESULTS: Higher abundance of Lachnospiraceae noname (OR = 0.86, 95% CI 0.81-0.91, P = 5.7 × 10 CONCLUSION: This study suggests that specific GM is causally associated with AAU risk, warranting more mechanistic validation and clinical trials.