The optical emission from a longitudinal dc glow discharge in water vapors (P=0.05–2.5 kPa) was studied in a wavelength range of λ=130–350 nm. It is shown that the discharge in low-pressure water vapors can be used as a source of the vacuum UV (VUV) radiation in the 140–190 nm wavelength range. As the vapor pressure was increased to 2.5 kPa, the emission intensity decreased by one-two orders of magnitude and the main peaks shifted to λ=286 and 306–315 nm. The bands of optical emission from the products of water decomposition agree in position with the emission band edges of the hydroxyl molecule. The obtained results are important for the development of a simple water-vapor electric-discharge VUV source.