In this review, we discuss liquid‐phase redox reactions using oxide solid‐solution catalysts. These oxide solid solutions are readily prepared by introducing various elements into the foundational metal oxide template. Doping with metal species leads to the formation of [MOx] clusters with unique coordination structures, which is a remarkable feature that deserves attention. Consequently, oxide solid solutions exhibit catalytic capabilities that extend beyond those of conventional metal‐oxide catalysts. Notably, these [MOx] clusters occasionally exhibit exceptional redox activities that can be used to catalyze liquid‐phase redox reactions. Hence, we conjecture that a connection exists between catalyst structure and activity. This review delves into oxide solid‐solution catalysts through the lenses of organic chemistry, solid catalysts, and computational chemistry, thereby collectively shaping our understanding and prospects in this field.