This paper investigates the productive efficiency of French regional rail operators. Benefiting from unique databases (2012-2016), we use a panel stochastic frontier model to measure and explain the productive efficiency. We consider the regional monopoly nature of these operators by introducing specific contract-related variables into the model. The technical efficiency level of regional operators ranges from 59 to 98 per cent, revealing a high degree of heterogeneity in productive performance between regional operators. Factors related to the societal environment (density and delinquency rate), the characteristics of the rail system (network length and number of stations) and contractual design are significantly correlated with the technical efficiency. The policy implications of these results are substantial for both public authorities and rail operators.