Evaporitic deposits constitute valuable archives of paleoenvironmental conditions in arid regions, where other sedimentary records are scarce. Reconstructing the salinity of parent brines from evaporite minerals, such as gypsum, is therefore essential for understanding past hydrological and climatic regimes. This study evaluates Brillouin spectroscopy as a non-destructive proxy for quantifying the salinity of fluid inclusions. Sound velocity measurements were performed on monophasic and biphasic fluid inclusions hosted in Middle Holocene gypsum from the el Melah sebkha (southeastern Tunisia) and were compared with bulk salinity estimates obtained by microthermometry. Calibration of sound velocity was achieved using a natural brine of known salinity, from which a range of solutions was produced through controlled evaporation and dilution experiments. The results reveal a robust linear relationship between sound velocity and salinity for both experimental brines (up to 320 g/ L) and gypsum-hosted fluid inclusions. Bulk salinities reconstructed by microthermometry range from 23.1 to 28.5 wt %, consistent with gypsum precipitation from modern marine-derived brines. Salinities derived from Brillouin sound velocity measurements closely match microthermometric estimates, with deviations of 0.5-1.3% using fluid inclusion calibration equations and 0.4-4.8% using synthetic brine calibrations. These results demonstrate that Brillouin spectroscopy provides a reliable and accurate proxy for salinity determination in gypsum fluid inclusions and offers significant advantages in systems where conventional microthermometry is time consuming and/or limited by metastability effects or complex brine compositions.