[en] VS₂ is a challenging material to prepare stoichiometrically in the bulk, and the single layer has not been successfully isolated before now. Here we report the first realization of single-layer VS₂, which we have prepared epitaxially with high quality on Au(1 1 1) in the octahedral (1T) structure. We find that we can deplete the VS₂ lattice of S by annealing in vacuum so as to create an entirely new 2D compound that has no bulk analogue. The transition is reversible upon annealing in an H₂S gas atmosphere. We report the structural properties of both the stoichiometric and S-depleted compounds on the basis of low-energy electron diffraction, x-ray photoelectron spectroscopy and diffraction, and scanning tunneling microscopy experiments. (paper)