[en] The electronic and geometrical structures of clusters formed by a single water molecule and small iron clusters Fe_n, Fe_n^-, and Fe_n⁺, for n=1-4, are studied using density functional theory. We found that FeH₂O and Fe₂H₂O possess a large number of isomers with different geometries, which are close in total energy to the corresponding ground states. In accord with previous computations, the ground state of FeH₂O has an inserted HFeOH geometry and water remains intact in the ground state of the FeH₂O⁺ cation. Beginning with Fe₂H₂O, the lowest energy states correspond to isomers with a fully dissociated water molecule, except for the ground state of the Fe₂H₂O⁺ cation that contains an OH group. Except for FeH₂O⁺ and Fe₄H₂O⁺, the hydrogen desorption energies (Fe_nH₂O->Fe_nO+H₂) are smaller than the water desorption energies (Fe_nH₂O->Fe_n+H₂O) for all neutral and ionic species considered and are relatively low, being about 1.5 eV