X-ray absorption fine structure (XAFS) spectroscopy was used to measure the Cl- and H2O coordination structure about Cu1+ in water at temperatures up to 325 degreesC including the coordination numbers, symmetry, distances and the amount of bond disorder. The linear dichloro Cu1+ species, [CuCl2](-), is especially stable and it is predominant from 100 degreesC to 325 degreesC in the presence of excess Cl-. Even for solutions with 2.0 m NaCl, only the dichloro Cu1+ species is observed with no evidence of higher Cl- coordination. There is no evidence of hydration waters in the first-solvation shell of this dichloro-species.