AbstractHigh-pressure Raman spectroscopy and x-ray diffraction of Sb₂S₃ up to 53 GPa reveals two phase transitions at 5 GPa and 15 GPa. The first transition is evidenced by noticeable compressibility changes in distinct Raman-active modes, in the lattice parameter axial ratios, the unit cell volume, as well as in specific interatomic bond lengths and bond angles. By taking into account relevant results from the literature, we assign these effects to a second-order isostructural transition arising from an electronic topological transition in Sb₂S₃ near 5 GPa. Close comparison between Sb₂S₃ and Sb₂Se₃ up to 10 GPa reveals a slightly diverse structural behavior for these two compounds after the isostructural transition pressure. This structural diversity appears to account for the different pressure-induced electronic behavior of Sb₂S₃ and Sb₂Se₃ up to 10 GPa, i.e. the absence of an insulator-metal transition in Sb₂S₃ up to that pressure. Finally, the second high-pressure modification appearing above 15 GPa appears to trigger a structural disorder at ~20 GPa; full decompression from 53 GPa leads to the recovery of an amorphous state.