Actinyl chemistry is extended beyond Cm to BkO2+ and CfO2+ through transfer of an O atom from NO2 to BkO+ or CfO+, establishing a surprisingly high lower limit of 73 kcal mol−1 for the dissociation energies, D[O‐(BkO+)] and D[O‐(CfO+)]. CCSD(T) computations are in accord with the observed reactions, and characterize the newly observed dioxide ions as linear pentavalent actinyls; these being the first Bk and Cf species with oxidation states above IV. Computations of actinide dioxide cations AnO2+ for An=Pa to Lr reveal an unexpected minimum for D[O‐(CmO+)]. For CmO2+, and AnO2+ beyond EsO2+, the most stable structure has side‐on bonded η2‐(O2), as AnIII peroxides for An=Cm and Lr, and as AnII superoxides for An=Fm, Md, and No. It is predicted that the most stable structure of EsO2+ is linear [O=EsV=O]+, einsteinyl, and that FmO2+ and MdO2+, like CmO2+, also have actinyl(V) structures as local energy minima. The results expand actinide oxidation state chemistry, the realm of the distinctive actinyl moiety, and the non‐periodic character towards the end of the periodic table.