A light guide plate includes: an optical glass, the optical glass having a refractive index nd of at least 1.75 or of at least 1.80 and including Nb2O5 in an amount of at least 15 mol % and P2O5 in an amount of at least 19 mol %, the light guide plate having an internal transmission of at least 0.80 or of at least 0.90, measured at a wavelength of 440 nm and a sample thickness of 10 mm.