Optical absorption peaks at 760 and 500 nm in LiNbO3 are assigned to oxygen vacancies containing one and two electrons, respectively. The 500-nm band appears after annealing above approximately 500 °C in a vacuum, i.e., a reducing atmosphere, and continues to grow with increasing anneal temperature. Optical bleaching near 77 K destroys the band at 500 nm and produces both a band at 760 nm and a Nb4+ electron spin resonance spectrum. The spectral dependence of the bleaching light required to convert the 500-nm band to the 760-nm band is determined.