Here we present a dataset of reconstructed daily river flow data relating to the Irish Hydrometric Reference Network Version 2 (IHRN V2), a database of high-quality gauging stations located across the Republic of Ireland. A combination of the GR4J conceptual hydrological model and a backpropagation neural network driven by catchment specific precipitation and temperature extracted from gridded datasets was used to reconstruct river flows from January 1941 till the end of 2022). Also included are the 2.5 and 97.5 quantile values for each station’s modelled data, which represent the upper and lower uncertainty bounds of the respective ensemble flows derived during the flow generation process. These reconstructions offer a useful means for identifying long term change in Irish river catchments and for evaluating the impact of climate change on Irish catchments and for assessing catchment based impacts for flow extremes.