Imidazole is a versatile heteroaromatic ring whose properties can be systematically tuned through substitution. N‐alkylation or N‐arylation yields imidazolium cations, which are frequently low‐melting and are then described as ionic liquids (ILs), and as precursors to N‐heterocyclic carbene (NHC) ligands. Substitution at the 4‐ and 5‐positions modulates the electronic and steric profiles of the five‐membered ring. Imidazole and imidazolium derivatives not only serve as solvents, catalysts, and cocatalysts in the reduction of CO 2 , but also act as electrolytes in dye‐sensitized solar cells (DSSCs) and as hole‐transport materials and multifunctional additives in perovskite solar cells (PSCs). Hence, the combination of imidazole/imidazolium‐based materials with versatile structures can bridge molecular design with high‐performance catalysis and photovoltaics. This mini‐review aims to survey imidazole/imidazolium‐scaffold structures and their applications in sustainable chemistry and energy conversion, providing a perspective on the structure–function relationships and future directions.