Treatment of an overcrowded triselenatribismane, 2,4,6-tris(bis(trimethylsilyl)methyl)phenyl-1,3,5-triselena-2,4,6-tribismane, with hexamethylphosphorous triamide in toluene at 100 degrees C resulted in the quantitative formation of a stable dibismuthene [TbtBi = BiTbt, where Tbt is 2,4,6-tris(bis(trimethylsilyl)methyl)phenyl], a compound containing a double bond formed between two bismuth atoms. The compound formed as deep purple crystals upon cooling. Ultraviolet-visible and Raman spectra, x-ray crystallographic structural analysis, and theoretical calculations provided evidence for the double bond character of the Bi-Bi bond.