Single crystalline bismuth oxide nanowires in the stable α and metastable β polymorphs were successfully synthesized by the vaporization of bismuth powders at 550-850 ℃ under a controlled oxidative atmosphere. Their diameters varied between 20-100 nm depending on the reaction conditions and their crystal structures. The lengths of these nanowires ranged from few micrometers to several tens of micrometers. The α and $β- Bi_2O_3$ nanowires were selectively synthesized by controlling the reaction conditions such as evaporation/deposition temperatures, and oxygen/argon flow rate. The assynthesized nanowires were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), photoluminescence (PL), and high temperature X-ray diffraction (HTXRD).