The data reduction process for the Lunar Prospector Gamma-Ray Spectrometer (LP-GRS) time series data is described. This process takes raw data that are received directly from the spacecraft and converts them to time series gamma-ray spectra that are used to derive elemental maps. These processed LP-GRS time series data are used as the fundamental data set for deriving composition measurements of the lunar surface using either energy window techniques or the full modeling of the neutron and gamma-ray transport processes. The analyses that use these gamma-ray spectra to derive elemental abundances are beyond the scope of this manuscript but are described elsewhere in multiple publications. The processing described here to create the time series gamma-ray spectra includes selections to eliminate bad data as well as make corrections due to time variations in the cosmic ray flux, LP-GRS gain, LP-GRS orientation, and altitude above the lunar surface. Descriptions are also given of data uncertainties and how the LP-GRS data are mapped onto the lunar surface.