PURPOSE: Predicting long-term outcomes after meningioma resection remains challenging. Ki-67/MIB-1 correlates with recurrence, yet its optimal cutoff is undefined. This study aims to establish a threshold that enhances risk stratification, improves recurrence prediction, and informs postoperative surveillance and adjuvant treatment strategies. METHODS: This is retrospective study of patients who underwent meningioma resection. Receiver operating characteristic (ROC) analysis determined the optimal MIB-1 cutoff for predicting recurrence and survival, providing area under the curve (AUC). This cutoff was then applied in Kaplan-Meier survival analyses and multivariable Cox regressions, controlling for age, sex, tumor diameter, tumor location, extent of resection, and adjuvant radiotherapy. RESULTS: A total of 404 patients were included. Median age was 55.0 years (range: 16-85) and 72.3% were female. The cohort primarily consisted of WHO Grade 1 (69.6%) and Grade 2 (30.0%) meningiomas. An optimal MIB-1 index cutoff of 4.1% was identified using ROC analysis with the Youden index for predicting recurrence (AUC = 0.661, p < 0.001) and survival (AUC = 0.717, p < 0.001). 241 patients (59.7%) had a MIB-1 < 4.1%, and 163 (40.3%) had a MIB-1 ≥ 4.1%. Patients with MIB-1 ≥ 4.1% had a higher risk of recurrence (HR = 2.9, p = 0.009) and mortality (HR = 2.8, p = 0.036). Patients with MIB-1 ≥ 4.1% demonstrated shorter recurrence-free survival (RFS) (119.0 vs. 129.0 months, p < 0.001) and overall survival (OS) (163.0 vs. 229.0 months, p < 0.001). CONCLUSION: We identified an optimal and actionable MIB-1 index cutoff of 4.1% which independently predicted recurrence, mortality, and shorter RFS and OS for patients undergoing meningioma resection. As the first study to establish and validate this threshold, our findings highlight its potential as an adjunct prognostic tool to refine risk stratification and guide postoperative management.