The synthesis, purification, and isolation of mononuclear Ru complexes containing the tridentate dianionic meridional ligand pyridyl‐2,6‐dicarboxylato (pdc²⁻) of general formula [Ru^III(pdc‐κ³‐N¹O²)(bpy)Cl] (1^III) and [Ru^II(pdc‐κ²‐N¹O¹)(bpy)₂] (2^II) (bpy is 2,2′‐bipyridine) is reported. These two complexes and their derivatives were thoroughly characterized through spectroscopic (UV/Vis, NMR) and electrochemical (cyclic voltammetry, differential pulse voltammetry, and coulometry) analyses, and three of the complexes were analyzed by single‐crystal X‐ray diffraction techniques. Under a high anodic applied potential, both complexes evolve towards the formation of Ru‐aquo/oxo derivative species, namely, [Ru^III(pdc‐κ³‐N¹O²)(bpy)(OH₂)]⁺ (1‐O) and [Ru^IV(O)(pdc‐κ²‐N¹O¹)(bpy)₂] (2‐O). These two complexes are active catalysts for the oxidation of water to dioxygen and their catalytic activity was analyzed through electrochemical techniques. A maximum turnover frequency (TOF_max)=2.4–3.4×10³ s⁻¹ was calculated for 2‐O.