Semiconductor nanowires have been received considerable attention in the past decade driven by both unprecedented physics derived from the quantum size effect and strong isotropy, and advanced applications as potential building blocks for nanoscale electronics and optoelectronic devices. Recently, organic-inorganic hybrid perovskites have been shown to exhibit high optical absorption coefficient, optimal direct band gap and long electron/hole diffusion lengths, leading to high performance photovoltaic devices. Herein, we present the vapor phase synthesis free-standing CH3NH3PbI3, CH3NH3PbBr3 and CH3NH3PbIxCl3-x perovskite nanowires with high crystallinity. These rectangular cross-sectional perovskite nanowires have good optical properties and long electron hole diffusion length, which ensure adequate gain and efficient optical feedback. Indeed, we have demonstrated optical-pumped room-temperature CH3NH3PbI3 nanowire lasers with near-infrared wavelength of 777 nm, low threshold of 11 μJ/cm2 and a quality factor as high as 405. Our research advocates the promise of optoelectronic devices based on organic-inorganic perovskite nanowires.