In situ Raman spectra of MnWO4 have been measured at high pressures up to 29.4 GPa and temperatures up to 1473 K. It is shown that a pressure-induced phase transition from the monoclinic to triclinic phase starts at about 17.7 GPa at room temperature, and the phase transition is confirmed to be reversible. A temperature induced melting from monoclinic to molten state starts at 1100 K and is completed at 1300 K. After cooling, molten MnWO4 recrystallizes into monoclinic MnWO4 crystals. (C) 2013 Elsevier B.V. All rights reserved.