Subwavelength confinement and active control of light is essential for nanoscale communication devices at visible frequencies that support large bandwidths.[1-5] Noble-metal nanostructures present an excellent platform for strongly confined optical waveguides [6-13] because of their ability to support surface plasmon polaritons (SPPs).[14] However, SPP propagation suffers from losses that seriously limit their application potential. [9] Although significant progress toward SPP loss compensation has been reported for various planar 2D waveguide structures,[15-20] as well as lasing involving strongly localized plasmon modes,[21,22] SPP gain in 1D nanoscale waveguides at visible frequencies is yet to be accomplished. Here, we report the first demonstration of gain for deep subwavelength confined SPPs (mode area = λ2/40) in chemically prepared silver nanowires (Ag NWs). We measured a gain coefficient of 270 cm-1 resulting in 14% loss compensation using a continuous-wave (cw) pump laser. These results are an important step toward total loss compensation for highly confined nanowire SPPs.