A systematic series of triarylbismuthane oxides was prepared in order to disclose their structure and reactivity, which have been compared with those of lighter pnictogen counterparts. X-ray crystallographic analysis of tris(2-methoxyphenyl)bismuthane oxide and tris(2-methoxyphenyl)stibane oxide revealed that they exist as dimers with a flat bis(μ-oxo) ring, implying that the polarized Bi+–O and Sb+–O bonds aggregate to attain electrostatic stabilization. In sharp contrast to their phosphorus, arsenic, and antimony counterparts, triarylbismuthane oxides are thermally unstable and possess a high oxidizing ability. In particular, the bismuthane oxides bearing ortho-substituted aryl ligands oxidized primary and secondary alcohols to aldehydes and ketones, respectively, with high efficiency under mild conditions.