The accomplishment of nanowelding typically requires the input of high energy, possibly causing appreciable damages to the brittle nanomaterial. Herein, we report an external field (EF, i.e., light, direct current (DC), and alternating current (AC))-strengthened Ostwald nanowelding (ONW) strategy to enable low-temperature nanowelding of Au nanoparticles (NPs) with nanoscale spacing in solution and propose an electron localization mechanism to understand it. We reveal that the EF-derived local electrons not only greatly strengthen the dissolution of surface atoms and the reduction of Au³⁺ ions dissolved, but also confine (together with ordered water molecules) the transport of Au³⁺ ions within the nanogap. Consequently, the electrochemical Ostwald ripening (OR) process of the Au NPs is actively strengthened, which, along with the local electron-strengthened surface atom diffusion (as a result of the strong electrostatic repulsion created), enables feasible ONW for solution processing of interdigital electrodes (IDEs) from Au NPs and high-performance transparent conductor (TC) from Ag nanowires (NWs). Our low-temperature nanowelding strategy offers an efficient interconnection technique for the processing of functional nanodevices from individual nanomaterials.