I present a discussion of fundamental stellar parameters and their observational determination in the context of interferometric measurements with current and future optical/infrared interferometric facilities. Stellar parameters and the importance of their determination for stellar physics are discussed. One of the primary uses of interferometry in the field of stellar physics is the measurement of the intensity profile across the stellar disk, both as a function of position angle and of wavelength. High-precision fundamental stellar parameters are also derived by characterizations of binary and multiple system using interferometric observations. This topic is discussed in detail elsewhere in these proceedings. Comparison of observed spectrally dispersed center-to-limb intensity variations with models of stellar atmospheres and stellar evolution may result in an improved understanding of key phenomena in stellar astrophysics such as the precise evolutionary effects on the main sequence, the evolution of metal-poor stars, stellar pulsation, mass-loss from high-mass main-sequence stars as well as from evolved stars, circumstellar environments, stellar magnetic activity, stellar rotation, and convection and turbulent mixing. Examples of already achieved results with existing interferometric facilities and anticipated improvements during the VLTI era are described. A science case for a next-generation optical/infrared interferometric facilities is presented, and the required specifications to achieve it are given. Finally, important synergy effects with external facilities in order to reach a more complete picture are discussed.

To appear in Proc. of the 37th Liege International Astrophysical Colloquium "Science Case for Next Generation Optical/Infrared Interferometric Facilities (the post VLTI era)"