Display omitted •Gigapascal pressure generates the second or further extended solvation of Cl–•Gigapascal compression transforms water’s tetrahedral network to a dense random packing.•Gigapascal pressure does not change the Na+ solvation structure.•Gigapascal pressure does not alter linear Cl…Dw–Ow and Ow…Dw–Ow bonds but broadened.•Gigapascal pressure does not alter the tilt angle about 31 °of solvated water dipole from the Na-Ow direction but broadened. An aqueous 3 m (=mol kg−1) NaCl solution in D2O is investigated at 0.1 MPa (hereafter denoted as 0 GPa)/298 K, 1 GPa/298 K, 1 GPa/523 K, and 4 GPa/523 K by neutron scattering combined with an empirical potential structure refinement (EPSR) method. The pressure and temperature dependence of the ion solvation and association and solvent water structure is discussed in pair correlation functions, coordination number distributions, angular distributions (orientational correlation), and spatial density functions (3D structure). The Na+ solvation is characterized as nearly octahedral coordination with about five water molecules and one Cl− over a pressure range measured. The Na–Ow (water oxygen) and Na–Dw (water hydrogen) distances are 2.34–2.37 Å and 2.82–3.00 Å, respectively. The water dipole is tilted by about 31° from the Na–O bond direction and the angle distribution becomes broader with an increase in pressure and temperature. The Cl− solvation shows a change in the coordination number of a water oxygen atom from 11 at 0 GPa to 15 at 4 GPa. An increase in the coordination number of a water hydrogen atom with pressure is observed; the values fall within five to six. The first neighbor Cl–Dw and Cl–Ow distances are 2.19–2.28 Å and 3.10–3.21 Å, respectively. The hydrogen-bonded angle Cl−···Dw–Ow is almost linear over a whole pressure range, but the angle distribution becomes broader upon compression. Another interesting finding of the Cl− solvation is the formation of extended solvation shells of Cl− in the gigapascal pressure range as if they behave as a structure making ion as Na+. The extended solvation shell of Cl– is caused by the breakdown or distortion of the hydrogen-bonded network of solvent water under compression. The coordination number of water oxygen increases from 4.7 at 0 GPa to 12–13, close to a value seen in simple liquids like Ar at 1–4 GPa. Despite such a drastic increase in water oxygen coordination number, the coordination number of the water hydrogen decreases from 2.2 at 0 GPa to 1.8 at 4 GPa, with the Ow–Dw distance lengthening from 1.77 Å to 1.95 Å, i.e., the hydrogen bonds between water molecules are retained in the gigapascal pressure range. The hydrogen bond angle Ow···Dw–Ow is almost linear, but the angle distribution is broadened upon compression, suggesting the distortion of the hydrogen bonds. Thus, it is concluded that compression of an aqueous NaCl solution to the gigapascal pressure causes the distortion of the hydrogen bonds between water molecules, resulting in the formation of the second and extended shells of a structure breaking Cl−.