In the search for new ionic liquids (ILs) for biomass processing, analytical chemistry, or modern nonvolatile fire retarding agents, alkyl phosphonate-based ILs represent very promising candidates. A very practical synthesis of such ILs, which is superior to the conventional quaternization of 1-alkylimidazoles by dimethyl phosphite (DMP), was developed. 1,3-Dialkylimidazolium halide salts serve as convenient starting materials, and various 1,3-dialkylimidazolium methyl phosphonates are thus accessible by simple, fast, and solvent-free procedures with DMP, where the anion is methylated.