A design for a passively phase-stable two-dimensional electronic spectroscopy experiment, based on a four-quadrant mirror concept, is introduced. The setup, which is particularly simple and robust, achieves subwavelength stability without the need for active stabilization or diffractive optical elements. Since only reflective optical components are used, the setup is suitable for few-cycle laser pulses and ultrabroad-bandwidth light in the ultraviolet, visible, and near-IR regions, with the capability to be used under grazing incidence for soft x ray or x-ray light at free-electron lasers.