Iridium dihydride complexes supported by PCP-type pincer ligands rapidly insert CO2 to yield kappa(2-)formate monohydride products in THF. In acetonitrile/water mixtures, these complexes become efficient and selective catalysts for electrocatalytic reduction of CO2 to formate. Electrochemical and NMR spectroscopic studies have provided mechanistic details and structures of key intermediates.