A new type of Ag/AgCl electrodes based on a hydrophobic ionic liquid has been proposed. The electrode consists of a Ag/AgCl electrode immersed in or coated with a AgCl-saturated ionic liquid, 1-methyl-3-octylimidazolium bis(trifluoromethylsulfonyl)imide ([C(8)mim+][C(1)C(1)N-]), instead of the internal aqueous solution. The [C(8)mim+][C(1)C(1)N-] phase plays dual roles, that is, as a medium dissolving AgCl and an ionic-liquid-type salt bridge upon contact with an aqueous solution. The gelation of the [C(8)mim+][C(1)C(1)N-] phase allows us to prepare coated-wire-type solid-state reference electrodes with a well-defined thermodynamic basis for the electrode potential. Both gelled and nongelled types show stable electrode potentials against the change in the concentration of KCl between 0.05 mmol dm(-3) and 2 mol dm(-3). This new class of reference electrodes opens the way for a variety of miniaturized and solid-state reference electrodes.