Ozone and inorganic ozonides are known to be very unstable in water and ozone oxidizes redox active transition metals to higher oxidation states while possible intermediate ozonides have not been isolated. Here, ozonation of a water soluble Co(II) substituted polyoxometalate, [a2-P2CoII(H2O)W17O61]8–[CoIIH2O], yielded an active species which isstable in cold waterfor hours. Reactivity studies of the active species with PBN and DMPO spin traps, and saturated and unsaturated water-soluble alcohols, including difficult to oxidize perfluorosubstituted alcohols confirm reactivity through C-H bond activation only. No oxidation of alkenes was observed.Decomposition stoichiometry as well as other probe experiments indicate the presence of a reactive tri-oxygen species, for example an ozonide, [a2‑P2CoIII(O3‑•)W17O61]8–[CoIIIO3].DFT calculations suggest an end-on ozone moiety in[CoIIIO3], a ~1 electron spin density on the 3 oxygen atoms of the O3–group and support radical type behavior with C–H bond activation rather than 1,3-dipolar addition to alkenes typical for O3itself.