The pressure/temperature phase diagram of LiAlH4 has been constructed by using Raman spectroscopy data. In situ high pressure−temperature experiments were carried out using resistively heated diamond anvil cells up to 150 °C and 7 GPa. Room temperature phase transitions of monoclinic α-LiAlH4 → δ-LiAlH4 were observed at ~3.2 GPa. As the temperature is increased to ~100 °C, both the α and δ phases transform to β-LiAlH4 and remain stable up to 5.5 GPa. At temperatures greater than 300 °C, a new γ-LiAlH4 phase forms. Data of Konovalov (1995) has been used to define the phase boundary between β- and γ-LiAlH4 phases. We present a pressure−temperature phase diagram of LiAlH4 based using diamond anvil cells coupled with Raman spectroscopy.