Organic-inorganic metal halide ferroelectric semiconductors are mainly lead halide ones, suffering from the presence of toxic lead. Herein, we report a lead-free bismuth iodide ferroelectric semiconductor [1,4-butanediammonium]BiI5, showing a high Curie temperature of 365 K and a small band gap of 1.95 eV, smaller than those of most lead halide counterparts.