Estimating low-flow indices is of paramount importance to understand low flows and to manage water resources and risk assessments. These indices are derived from time-series of river discharges which are measured at gauged sites over long periods. However, the indices must be estimated at ungauged sites. Different estimation methods exist to estimate these low-flow indices from observed discharges in neighbouring catchments and from catchment characteristics. Regression or geostatistical methods performed on the low-flow indices are the most common types of methods. Another less common method consists in regionalizing rainfall-runoff model parameters, from catchment characteristics or by spatial proximity, to estimate low-flow indices from simulated hydrographs. We developed a conceptual daily rainfall-runoff model, LoiEau, combined with a regionalized model of snow storage and melt, to simulate low-flow indices at daily or longer time intervals. This model relies on two free parameters, which is sufficient to provide accurate enough estimates of low-flow indices, yet making easier the regionalization of the model. The model is flexible in the sense that it is designed to fit to a wide variety of catchments and hydro-meteorological behaviors, including Mediterranean catchments. The aim of this work is to regionalize the two parameters of the LoiEau model in order to estimate any low-flow indices at ungauged sites. Two regional methods are tested and are based on geostatistical and regression models. The first method is the inverse distance weighting to estimate the parameter sets from the neighbouring catchments and the second one is the regional regression method. This last method is based on relationships between the parameter sets and optimal sets of catchment characteristics established using forward stepwise linear regression for homogeneous regions. The chosen regions are hydro-eco-regions that are homogeneous in terms of geology, relief and climate. The analysis is carried out on 700 French catchments that are representative of various hydro-meteorological behaviours, with a focus on the Mediterranean hydro-eco-region. The results are validated with a cross-validation procedure and are compared, on the one hand, with the ones obtained with a regional regression model performed on a specific low-flow index and, on the other hand, with the ones obtained with a regionalized monthly rainfall-runoff model to show the advantage of a daily time step to account for the temporal variability of precipitations.