氡有34个已知的同位素，均具有放射性，其中最稳定的为Rn。

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。

There are 39 known isotopes of radon (Rn) from Rn to Rn; all are radioactive. The most stable isotope is Rn with a half-life of 3.823 days. Four isotopes, Rn occur in trace quantities in nature as decay products of, respectively, At, Ra, Ra, and Ra. Rn and Rn are intermediate steps in the decay chain for U, Rn is an intermediate step in the decay chain for U and Rn occurs in the decay chain for Th.