Relevant thermochemical data of gamma-butyrolactone (GBL), a compound of considerable industrial and environmental significance, obtained from experimental and computational studies are reported in this work. The standard (p degrees = 0.1 MPa) molar enthalpy of formation, at T = 298.15 K, in the gaseous phase, was determined from the enthalpy of combustion and vaporization, obtained by static bomb calorimetry in oxygen and by Calvet microcalorimetry, respectively. The enthalpy of formation in the gaseous phase was also determined from G3 calculations. The excellent agreement between the experimental and computational thermochemical data provided a critical literature review of GBL and the proposal of new reference values for this lactone.