Chalcopyrite copper indium sulfide (CuInS2) is an important semiconductor with a bandgap optimal for terrestrial solar energy conversion. Building photovoltaic and microelectronic devices using one-dimensional CuInS2 nanowires can offer directional conduits for rapid and undisrupted charge transport. Currently, single-crystal CuInS2 nanowires can be prepared only using vapor-based methods. Here, we report, for the first time, the synthesis of single-crystal CuInS2 nanowires using a microwave-assisted solution-liquid-solid (MASLS) method. We show that CuInS2 nanowires with diameters of less than 10 nm can be prepared at a rapid rate of 33 nm s-1 to more than 10m long in less than 10 min, producing a high mass yield of 31%. We further show that the nanowires are free of structural defects and have a near-stoichiometric composition. The success of MASLS in preparing high-quality tertiary nanowires is explained by a eutectic growth mechanism involving an overheated alloy catalyst.