Background: Improvements in risk stratification of meningioma are needed to guide post-operative management and application of adjuvant therapy. Although profiling of DNA methylation, copy number variants (CNVs), RNA sequencing, and exome sequencing have better elucidated meningioma biology, these approaches have not revealed clinically tractable biomarkers for radiotherapy responses. In this study, we develop and validate a targeted gene expression biomarker to predict meningioma outcomes and benefit from radiotherapy. Methods: Targeted gene expression profiling was performed on a development set of 173 meningiomas (median follow-up 8.1 years) and a validation set of 331 consecutive meningiomas (median follow-up 6.1 years) treated at independent institutions (70% WHO grade 1, 24% WHO grade 2, 6% WHO grade 3). All patients underwent surgery (n = 504) with or without postoperative radiotherapy (n = 73 with radiation). Regularized Cox regression within the development set resulted in a continuous gene expression risk score for local freedom from recurrence (LFFR). The model (34 genes and 7 housekeeping genes) and thresholds for low, intermediate, and high-risk scores were locked and applied to the validation set. Results: The gene expression risk score outperformed WHO grade (validation 5-year LFFR delta-AUC 0.15, 95% CI 0.076-0.229, p = 0.001) and DNA methylation grouping (delta-AUC 0.075, 95% CI 0.006-0.130, p = 0.01) for LFFR, disease-specific survival, and OS, achieving a negative predictive value for recurrence at 5-years of 93.2%. The biomarker reclassified 35.8% of WHO grade 1 tumors as intermediate or high risk (5-year LFFR/OS 62%/79%), and 18.3% of WHO grade 2-3 tumors as low risk (5-year LFFR/OS 78%/100%). The biomarker was independently prognostic after accounting for WHO grade, extent of resection, primary versus recurrent presentation, CNV status, DNA methylation group, and Ki67 labeling index, and was predictive for LFFR after postoperative radiotherapy, with a hazard ratio of 0.41 for intermediate to high risk propensity-matched meningiomas (95% CI 0.2-0.9, p = 0.0002) versus 0.79 for low risk meningiomas (95% CI 0.1-8.8, p = 0.5182). Conclusions: Targeted gene expression profiling of 504 meningiomas resulted in a biomarker which improved discrimination of meningioma local recurrence, disease-specific survival, and overall survival, and also predicted benefit from radiotherapy.