The title compound, Ir2H2O(C3H9P)62·2H2O, was isolated from the reaction between [Ir(COD)(PMe3)3]BF4 and H2 in water (COD is cyclo-octa-1,5-diene). The asymmetric unit consists of one Ir(III) atom bonded to three PMe3 groups, one hydride ligand and half an oxide ligand, in addition to a BF4 (-) counter-ion and one water molecule of hydration. The single oxide ligand bridging two Ir(III) atoms is disordered across an inversion center with each O atom having a 50% site occupancy. Each Ir(III) atom has three PMe3 groups occupying facial positions, with the half-occupancy O atoms, a hydride ligand and an Ir-Ir bond completing the coordination sphere. The Ir-Ir distance is 2.8614 (12) Å, comparable to other iridium(III) metal-metal bonds. Two water mol-ecules hydrogen bond to two BF4 (-) anions in the unit cell.