Water in site: The structure of a stable adduct of a peptide‐based nickel superoxide dismutase model (NiSOD) with cyanide as substrate analogue is determined by NMR spectroscopy and optimized by DFT methods. A functional water molecule is found in the active site (see picture; Ni brown, O red/pink, C green, N blue). The role of this water molecule in the catalytic degradation of O2.− is discussed.