Defect engineering has recently gained considerable interest in electrocatalysis by extending the portfolio of materials’ design strategies toward more efficient and sustainable nanocatalysts.(1) This approach is highly versatile as the term “defect” in crystallography refers to any interruption of the regular pattern defining a perfect crystal. As such, point defects (atomic vacancies, interstitial atoms, antisite defects), line defects (dislocations, disclinations), planar defects (grain boundaries, stacking faults, twinning, steps), or bulk defects (voids, pores, cracks) are a nonexhaustive list of structural parameters to be possibly tailored to meet a catalytic material’s functional specifications. In contrast to former approaches in electrocatalysis, within the defects’ engineering strategies, electrocatalytic properties are tuned locally not globally. Indeed, defects produce (simultaneous) local changes in key structural parameters relative to catalytic performance, such as site coordination, strain, or chemical composition.