The primary localization process of radiation-induced charges (holes [cationic radical sites] and excess electrons) remains poorly understood, even at the level of monomeric DNA/RNA models, particularly in an aqueous environment. We report the first direct observation of charge transfer occurring during the radiolysis of aqueous solutions of uridine 5′-monophosphate (UMP) and its components (Figure): uridine, uracil, ribose, and phosphate. Our results show that unsolvated electrons efficiently attach to the base site of UMP; the holes in UMP, formed either by direct ionization or by the reaction of UMP with the water cation radical (H2O°+) under radiation, easily localize at the ribose site, despite some being initially created at the phosphate or uracil sites. The nature of hole transfer from the phosphate to the sugar is characterized as an intramolecular electron transfer without a barrier, with a time constant of 2.5 ns, while hole transfer from the base to the sugar occurs much more rapidly, in less than 5 ps. These ultrafast charge transfers control the subsequent chemistry in the biological medium [Ma2018c, Delalande2021].