Solubility data of solid 3,4,5-trihydroxybenzoic acid (gallic acid) in supercritical CO2 + ethanol as a cosolvent are reported in this work. Measurements were carried out in the temperature range (313.15 to 333.15) K, pressures ranging from (10 to 40) MPa, and different ethanol modifier content ranging from (0.7 to 6) %. The experimental data were correlated using the Soave-Redlich-Kwong equation of state and the group contribution associating equation of state. The thermodynamic modeling analysis includes also the solubility representation of an important class of natural antioxidants (e.g., gallic acid esters) in supercritical CO2.