A temperature-dependent linear solvation energy relationship (LSER) is proposed for estimating the gas-to-ionic liquid partition coefficients. The model calculates the LSER parameters using a group contribution method. Large sets of partition coefficients were analyzed using the Abraham solvation parameter model to determine the contributions of 21 groups: 12 groups characterizing the cations and 9 groups for the anions. The derived equations correlate the experimental gas-to-ionic liquid coefficient data to within 0.13 log units. The 21 group parameters are used to predict the partition coefficients of solutes in alkyl or functionalized ionic liquids with good accuracy.