AbstractTransition metal‐based oxyhydroxides (MOOH) derived from the irreversible structural reconstruction of precatalysts are often acknowledged as the real catalytic species for the oxygen evolution reaction (OER). Typically, the reconstruction‐derived MOOH would exhibit superior OER activity compared to their directly synthesized counterparts, despite being fundamentally similar in chemistry. As such, structural reconstruction has emerged as a promising strategy to boost the catalytic activity of electrocatalysts. However, the in‐depth understanding of the origin of the superior OER activity of reconstructed materials still remains ambiguous, which significantly hinders the further developments of highly efficient electrocatalysts based on structural reconstruction chemistry. In this review, a comprehensive overview of the structural reconstruction behaviors in the reported reconstruction‐derived electrocatalysts is provided and the intrinsic chemical and structural origins of their high efficiency toward OER are unveiled. The fundamentals of structural reconstruction mechanisms, along with the recommended characterization techniques for the understanding of the dynamic structural reconstruction process and analyzing the structure of real catalytic species are also interpreted. Finally, in view of structural reconstruction chemistry, the potential perspectives to facilitate the design and synthesis of highly efficient and durable OER electrocatalyst are presented.