[HIrIVW6O24]7−, representing the first Ir-containing Anderson–Evans-type polyanion and the first structurally characterized IrIV-based polyoxometalate, has been isolated as its hydrated sodium salt and characterized by single-crystal X-ray diffraction, mass spectrometry, and IR, UV-Vis and EPR spectroscopy. Cyclic voltammetry indicates that the IrIV ions in [HIrW6O24]7− can undergo reversible one-electron reduction and oxidation, resulting in IrIII and IrV derivatives