Water/oil emulsions are formed in oil wells because of the presence of natural surfactants, such as asphaltenes and resins. These molecules strongly stabilize the water/oil interface and prevent coalescence of water droplets. Because water/oil phase separation is necessary before oil refining, surfactants are used to break water/oil emulsions. Herein, surface-active ionic liquids were synthesized and evaluated for the first time as demulsifier agents for water-in-crude oil emulsions of light, heavy, and ultra-heavy Mexican crude oil under conventional and microwave dielectric heating. The use of microwave irradiation accelerated and increased significantly the efficiency of demulsification of ultra-heavy crude oil emulsion.