We report a scanning tunnelling microscopy (STM) study of the surface morphology of Au(111) exposed to oxygen at high temperature (700-800°C) and high pressure (1 bar). Two types of oxygen induced surface structures were observed: (i) a hexagonal long-range reconstruction with a periodicity of ∼ 65 and a corrugation of about 0.5 . At the atomic scale this surface exhibits a (√3 √3)R30° structure, which we attribute to atomic oxygen strongly chemisorbed at the Au(111) surface. (ii) a @'modified@' herringbone pattern related to the original herringbone reconstruction of the clean Au(111) surface, but with additional depressions in some of the fcc-regions between the reconstruction lines. At the atomic scale this surface exhibits a characteristic @'row structure@' with √3 periodicity. For both structures the dependence of the STM image contrast on the tunnelling parameters was investigated.