A novel process for the electrochemical atomic layer etching (e-ALE) of copper (Cu) is presented. In this process, Cu first undergoes surface-limited sulfidization to form a monolayer of copper sulfide (Cu2S). The Cu2S layer is then selectively etched in hydrochloric acid without etching the underlying Cu. The steps of surface-limited sulfidization of Cu and selective etching of the resulting Cu2S are repeated sequentially to achieve a net etch rate of close to one Cu monolayer etched per e-ALE cycle. Surface-limited etching is shown to minimize roughness amplification thereby preserving the near-atomic flatness of the original Cu electrode. (C) The Author(s) 2018. Published by ECS.