Copper nanowires (Cu NWs) have attracted increasing attention as building blocks for electronics due to their outstanding electrical properties and low cost. However, organic residues and oxide layers ubiquitously existing on the surface of Cu NWs impede good inter-wire contact. Commonly used methods such as thermal annealing and acid treatment often lead to nanowire damage. Herein, hydrogen plasma treatment at room temperature has been demonstrated to be effective for simultaneous surface cleaning and selective welding of Cu NWs at junctions. Transparent electrodes with excellent optical-electrical performance (19 Omega.sq(-1) @ 90% T) and enhanced stability have been fabricated and integrated into organic solar cells. Besides, Cu NW conductors with superior stretchability and cycling stability under stretching speeds of up to 400 mm.min(-1) can also be produced by the nanowelding process, and the feasibility of their application in stretchable LED circuits has been demonstrated.