The development of economic water oxidation catalysts is a key step toward large-scale water splitting. However, their current exploration remains empirical to a large extent. Elucidating the correlations between electronic properties and catalytic activity is crucial for deriving general and straightforward catalyst design principles. Herein, strongly correlated electronic systems with abundant and easily tunable electronic properties, namely La1–xSrxBO3 perovskites and La2-xSrxBO4 layered perovskites (B = Fe, Co, Ni, or Mn), were employed as model systems to identify favorable electronic structures for water oxidation. We established a direct correlation between the enhancement of catalytic activity and the insulator to metal transition through tuning the electronic properties of the target perovskite families via the La3+/Sr2+ ratio. Their improved photochemical water oxidation performance was clearly linked to the increasingly metallic character. These electronic structure–activity relations provide a promising guideline for constructing efficient water oxidation catalysts.