We observe ultraviolet-light-induced absorption changes in spectral regions from the near-ultraviolet to the near-infrared in as-grown LiNbO3: Mg. Such a broad light-induced absorption band is unstable at room temperature and decays nonmonoexponentially in the dark with a time constant on the order of tens of seconds.We attribute the appearance of the broadband light-induced absorption to the creation of the intermediate state O2 in which holes excited from deep defect centers are trapped at O22 sites near cation vacancies. It is also found that near-infrared photorefractive sensitivities increase by several orders of magnitude by pre-exposing the crystal to incoherent ultraviolet light. These properties may be useful for an application of LiNbO3: Mg to nonvolatile two-color holography.