The GPM Ground Validation Dual-frequency Dual-polarized Doppler Radar (D3R) OLYMPEX dataset contains radar reflectivity, velocity, differential reflectivity, differential phase, spectrum width, and co-polar correlation products collected during the Global Precipitation Measurement mission (GPM) Ground Validation (GV) Olympic Mountains Experiment (OLYMPEX). The OLYMPEX field campaign took place between November 2015 and January 2016, with additional ground sampling continuing through February 2016, on the Olympic Peninsula in the Pacific Northwest of the United States. The purpose of the campaign was to provide ground-validation data for the measurements taken by instrumentation aboard the GPM Core Observatory satellite. The Dual-frequency Dual-polarized Doppler Radar (D3R) was developed by a government-industry-academic consortium with funding from NASA’s GPM mission and was used in several ground validation projects. D3R operates at the Ku-band (13.91 GHz ± 25 MHz) and Ka-band (35.56 GHz ± 25 MHz) frequencies, similar to the frequencies used for the GPM satellite instruments, and covers a fixed range from 450 m to 40 km. For OLYMPEX, the D3R was co-located with the NASA S-band Dual Polarimetric (NPOL) Doppler Radar at a coastal Washington state location on the Olympic Peninsula. Due to blockage caused by NPOL, the D3R measurement area is limited to a 220 degree to 120 degree sector. The GPM GV D3R OLYMPEX dataset files are available from November 8, 2015 through January 15, 2016 in netCDF-4 format along with browse imagery of reflectivity in PNG format.