Field emission from vertically aligned free-standing copper nanowires (CuNWs) is reported. The CuNWs were grown by chemical vapor deposition on various substrates without using templates, catalysts or lithographic processes. The nanowires exhibited excellent field emission characteristics that are comparable to carbon nanotubes and other nanowires, and are substantially superior to those CuNWs prepared by template method. Different substrates, electrode distances and pressures were tested. Low turn-on fields and high field-enhancement factors were obtained of the emitters and their robustness and long-term stability demonstrated. These results suggest that the present CuNWs may serve as viable emitters for practical applications.