Intense broadband emission in the visible is observed from crystals of Bi4Ge3O12under optical and x‐ray excitation. From measurements of absorption, reflection, fluorescence, and excitation spectra, the emission is assigned to3P1→1S0transitions of Bi3+. The Stokes shift is large,[inverted lazy s]14 000 cm−1. The temperature dependences of the fluorescence intensity and lifetime in the range 77–400 °K establish that nonradiative decay becomes significant at temperatures ⪞250°K. Comparison of the properties of Bi4Ge3O12with those of Bi12GeO20and other bismuth‐activated materials demonstrates the importance of the Stokes shift and the1S‐3Penergy difference in determining the luminescence behavior. The use of Bi4Ge3O12as a laser host crystal for rare‐earth and iron group activator ions, and as a scintillator material is discussed briefly.