This perspective article reports the most significant advances in the field of water oxidation—from molecular water oxidation catalysts (WOCs) to photoelectrochemical cells. Different series of catalysts that can be applied in visible light-driven water oxidation catalysis are discussed in details and several key aspects of their catalytic mechanisms are introduced. In order to construct a water oxidation electrode from molecular catalysts, proper immobilization methods have to be employed. Herein, we present one section about how to attach catalysts onto an electrode/material surface. Finally, the state of the art photoelectrochemical cells that achieve visible light-driven water splitting are described.