The paper describes a reactor suitable for high pressure, particularly supercritical fluid, electrochemistry and electrodeposition at pressures up to 30 MPa at 115 degrees C. The reactor incorporates two key, new design concepts; a plastic reactor vessel and the use of o-ring sealed brittle electrodes. These two innovations widen what can be achieved with supercritical fluid electrodeposition. The suitability of the reactor for electroanalytical experiments is demonstrated by studies of the voltammetry of decamethylferrocene in supercritical difluromethane and for electrodeposition is demonstrated by the deposition of Bi. The application of the reactor to the production of nanostructures is demonstrated by the electrodeposition of similar to 80 nm diameter Te nanowires into an anodic alumina on silicon template. Key advantages of the new reactor design include reduction of the number of wetted materials, particularly glues used for insulating electrodes, compatability with reagents incompatible with steel, compatability with microfabricated planar multiple electrodes, small volume which brings safety advantages and reduced reagent useage, and a significant reduction in experimental time. (C) 2017 The Electrochemical Society. All rights reserved.