Interest in ionic liquids with guanidine, amidine and other superbasic cations has grown markedly in recent years. The syntheses, characterization and properties of protic and quaternary alkylated salts based on cyclic or acyclic guanidine and amidine derivatives have been described in detail. By modifying the anion or the cation, a wide range of properties of superbasic ionic liquids can be tuned, including viscosity, melting point, density, conductivity, solubility, liquid range, and thermal and hydrolytic stability. They are promising solvents for electrochemical, photovoltaic and various synthetic applications, in particular as specific catalysts. Owing to their specific properties, superbasic ionic liquids can be used in applications of great industrial importance such as CO₂, SO₂ or COS chemisorption.