Solubility data of carbon dioxide, propane, propene, butane, and 1-butene in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([ bmim][ Tf2N]) are presented as a function of pressure at temperatures between 280 K and 340 K. The equilibrium pressure at a given temperature and the amount of gas dissolved into the ionic liquid phase were measured with an experimental technique based on a saturation method at constant volume by use of an apparatus equipped with a cylindrical equilibrium view cell. All measured solubilities were between 0.1 and 0.5 mole fraction gas in ionic liquid. 1-Butene had the highest solubility, followed by butane, propene, and then propane. Carbon dioxide and propane are similarly the least soluble in the [ bmim][ Tf2N]. Alkene gases were more soluble than alkane gases. From the experimental solubility data, the Henry's constants of each gas in the ionic liquid were estimated as a function of temperature.