The classic liquid filled reference electrode is unreliable while operating within harsh environments where high temperatures and pressures are commonly encountered. A rugged, reliable, solid-state reference electrode which is not dependent upon a liquid element could prove to be a beneficial technological advance. This report presents the method of construction and test results of an experimental solid-state reference electrode built upon a graphene/graphite substrate which was evaluated using four different analytical methods-Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Chronopotentiometry (Galvanostatic), and Potentiometry. The potentiometric, impedance, and galvanostatic studies examined the response of the experimental electrode at temperatures ranging from 293 K–473 K (20 °C–200 °C) and pressures exceeding 55 bar. The electrode response was tested in aqueous solutions of potassium iodide and potassium chloride with concentrations ranging from 1 to 1·10⁻⁵ mol L⁻¹. The reference cell was evaluated against eight criteria points which a reliable, thermodynamically reversible, reference electrode is required to meet or exceed. These experimental electrodes provisionally passed seven of the eight criteria points and are constructed of materials which are both physically and chemically resilient. The observed potential remained stable during the initial long term observational study which exceeded 2500 consecutive operational hours. These electrodes have been shown to be thermodynamically complementary, reversible, and Nernstian.