The structure of the clean Pt(111) surface has been studied between 300 K and 0.92${\mathit{T}}_{\mathit{m}}$ (${\mathit{T}}_{\mathit{m}}$=2045 K) via x-ray scattering. The surface is unreconstructed for temperatures less than 0.65${\mathit{T}}_{\mathit{m}}$, but reconstructs at higher temperatures to form a layer isotropically compressed and incommensurate with the underlying bulk (111) planes. A disordered arrangement of discommensurations separates regions with ideal fcc stacking from regions with faulted stacking. With increasing temperature, both the compression of the surface layer and the orientational order of the discommensurations increase.