铋（原子量：208.98040(1)）的同位素

备注：画上#号的数据代表没有经过实验的证明，只是理论推测而已，而用括号括起来的代表数据不确定性。

Bismuth (Bi) has no stable isotope, but does have one very long-lived isotope; thus, the relative atomic mass can be given as 208.9803987(16). Although bismuth-209 is now known to be unstable, it has classically been considered to be a "stable" isotope because it has a half-life of over 1.9×10 years, which is more than a billion (1000 million) times the age of the universe. Besides Bi, the most stable bismuth radioisotopes are Bi with a half-life of 3.04 million years, Bi with a half-life of 368,000 years and Bi, with a half-life of 32.9 years, none of which occur in nature. All other isotopes have half-lives under 1 year, most under a day. Of naturally occurring radioisotopes, the most stable is radiogenic Bi with a half-life of 5.012 days.