Graphene-based terahertz (THz)-field-induced optical luminescence (GB-TFIOL) is proposed in this Letter as a novel, to the best of our knowledge, THz imaging technique. We experimentally show that two-dimensional distribution of the optical luminescence from a monolayer graphene traces the beam profile of the pump THz radiation. The atomic thickness of a graphene detector, as well as a strong nonlinear dependence of optical luminescence on THz field, make the GB-TFIOL technique a useful tool for near-field mapping. A proof-of-principle experiment of the visualization of local THz-field enhancement near a metal tip with a 2 µm radius curvature was performed.