The atomic-scale structural changes in an α-Fe 2 O 3 (hematite) (0001) surface induced by sulfidation and subsequent oxidation processes were studied by X-ray photoemission spectroscopy, LEED, and X-ray standing wave (XSW) measurements. Annealing the α-Fe 2 O 3 (0001) with a H 2 S partial pressure of 1×10 −7 Torr produced iron sulfides on the surface as the sulfur atoms reacted with the substrate Fe ions. The oxidation state of the substrate Fe changed from 3+ to 2+ as a result of the sulfidation. The XSW measured distance of the sulfur atomic-layer from the unrelaxed substrate oxygen layer was 3.16Å. The sulfide phase consisted of three surface domains identified by LEED. Formation of the two-dimensional FeS 2 phase with structural parameters consistent with an outermost layer of (111) pyrite has been proposed. Atomic oxygen exposure oxidized the surface sulfide to a sulfate (SO42-) and regenerated the α-Fe 2 O 3 (0001) substrate, which was indicated by a (1×1) LEED pattern and the re-oxidization of Fe to 3+.