Abstract: Bench-scale tests were conducted to investigate the ozonation of Microcystin (MC)-RR obtained from cyanobacterial blooms in this study. The effects of ozone dose, initial MC-RR concentration, solution pH, and coexisting anions on the MC-RR ozonation kinetics were evaluated. Results showed that the MC-RR ozonation well followed the pseudo-first-order degradation kinetics under different experimental conditions. At pH 7 and 461.5 μg/L MC-RR, the degradation rate constant dramatically increased from 0.0125 to 0.0623 min−1 with the increase of the ozone dose from 0.31 to 1.35 mg/L, but was not significantly affected by the initial MC-RR concentration. Typically, an acidic condition favored the MC-RR degradation. As the pH increased from 3.1 to 10.1, the rate constant decreased from 0.1906 to 0.0102 min−1 at an O3 dose of 0.82 mg/L. Different inorganic anions exhibited different behaviors in the MC-RR degradation. (Formula presented.) slightly enhanced the decomposition, while (Formula presented.) , Cl−, and (Formula presented.) slowed the degradation to different degrees. Particularly, the inhibiting effect of (Formula presented.) was significant, probably due to its scavenging effect. These results demonstrated that ozonation appears to be a promising treatment method in the removal of MC-RR from water sources.