Air−water interfacial retention of poly-and perfluoroalkyl substances (PFASs) is increasingly recognized as an important environmental process. Herein, column transport experiments were used to measure air−water interfacial partitioning values for several perfluoroalkyl ethers and for PFASs derived from aqueous film-forming foam, while batch experiments were used to determine equilibrium K ia data for compounds exhibiting evidence of rate-limited partitioning. Experimental results suggest a Freundlich isotherm best describes PFAS air−water partitioning at environmentally relevant concentrations (10 1 −10 6 ng/L). A multiparameter regression analysis for K ia prediction was performed for the 15 PFASs for which equilibrium K ia values were determined, assessing 246 possible combinations of 8 physicochemical and system properties. Quantitative structure−property relationships (QSPRs) based on three to four parameters provided predictions of high accuracy without model overparameterization. Two QSPRs (R 2 values of 0.92 and 0.83) were developed using an assumed average Freundlich n value of 0.65 and validated across a range of relevant concentrations for perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), and hexafluoropropylene oxidedimer acid (i.e., GenX). A mass action model was further modified to account for the changing ionic strength on PFAS air−water interfacial sorption. The final result was two distinct QSPRs for estimating PFAS air−water interfacial partitioning across a range of aqueous concentrations and ionic strengths.