The GPM Ground Validation Dual-frequency Dual-polarized Doppler Radar (D3R) IFloodS dataset contains radar reflectivity and doppler velocity measurements from the Iowa Flood Studies (IFloodS) campaign. This campaign aimed to improve satellite precipitation measurements for flood prediction by using ground measurements to improve satellite retrieval algorithms. The D3R was developed by a government-industry-academic consortium with funding from NASA's Global Precipitation Measurement (GPM) Project. It operates at the ku (13.91 GHz ± 25 MHz) and ka (35.56 GHz ± 25 MHz) frequencies covering a fixed range from 450 m to 39.75 km. The D3R IFloodS dataset is available from May 9, 2013 through June 13, 2013 in netCDF-3 format with corresponding browse imagery available in PNG format.