Powder x-ray diffraction data for FeS polymorphs were collected at high pressure and temperature, using monochromatic synchrotron x-radiation and image plate. The diffraction data collected at 10. 95 GPa and 300 K revealed a monoclinic high-pressure phase (FeS III) with cell parameters, a = 8. 025 (4) Å, b = 5. 614 (2) Å, c = 6. 414 (4) Å, and β=93. 01 (4) º. The space group of this monoclinic phase is P2₁/a . We also collected diffraction data for the high PT phase (FeS IV) at 5. 2 GPa and 9. 0 GPa and at 530 K and for the high-T phase (FeS V) at 3. 4 GPa and 650 K. The FeS IV phase has a hexagonal (2a, c) unit cell (space group P6₃mc) and the FeS V phase has a simple NiAs-type structure (space group P6₃/mmc). The structure parameters were determined by Rietveld refinements.