Ultrathin iridium nanowires have been synthesized using a convenient method mediated by microemulsion via oriented attachment growth for the first time. The interconnected polycrystalline Ir nanowires possess high aspect ratio, small average diameter of 2 nm, and length up to several hundred nanometers. The 1D growth of surfactant-encapsulated primary nanoparticles, which is determined by the inherent crystal growth habit and the specific interactions of nanocrystals with surfactant molecules, accounts for the formation of Ir nanowires. The as-prepared Ir nanowires show high activity and selectivity toward the hydrogenation production of industrially valuable chloroaniline from o-chloronitrobenzene. Theoretical evidence based on DFT calculation indicates that H2 could be dissociated more easily and quickly on Ir(100) surface than on Ir(111), accounting for the higher hydrogenation rate over Ir nanowires exposing both (200) and (111) crystal facets rather than only (111) facet for Ir nanoparticles.