Large-scale vapor-solid synthesis of ultralong silicon nitride (Si3N4) nanowires was achieved by using simple thermal evaporation of mixture powders of active carbon and monoxide silicon. The products were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The results suggest that the silicon nitride nanowires have a smooth surface, with lengths of up to several hundreds of microns and diameters of 100-300 nm. A detailed study of both the chemical and structural composition was performed. Such ultralong silicon nitride nanowires demonstrate potential applications as materials for constructing nanoscale devices and as reinforcement in advanced composites. Large-scale vapor-solid synthesis of ultralong silicon nitride (Si3N4) nanowires was achieved by using simple thermal evaporation of mixtures of powders of active carbon and monoxide silicon. The products were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X -ray spectroscopy, and transmission electron microscopy. The results suggest that the silicon nitride nanowires have a smooth surface, with lengths of up to several hundreds of microns and diameters of 100-300 nm. A detailed study of both the chemical and structural composition was Such ultralong silicon nitride nanowires demonstrate potential applications as materials for constructing nanoscale devices and as reinforcement in advanced composites.