One of the key requirements for the reduction of the overall environmental impact of a chemical process is the replacement of organic solvents with more benign reaction media like water, however this suffers from solubility limitations. A powerful tool to overcome these issues in synthesis is micellar catalysis, where a small amount of surfactant species form aggregates in water with a lipophilic core that can act as a nanoreactor. Surface-active ionic liquids are prime candidates for this application due to the tunability of structure and properties of conventional ionic liquids that have already been established in catalysis. This thesis provides fundamental insight into the nature of self-organization of surface-active ionic liquids in water, with special focus on the design, development and evaluation of new ionic liquids-water micellar systems and their application in synthesis and catalysis. The synthesis of a series of new 1-dodecylimidazolium based surface-active ionic liquids with different structural features is reported, as well as their surface-activity characterization. In order to test the broad applicability of ionic liquids-water micellar systems as reaction media different types of transformations have been tested. âOrganic synthesis: the influence of surface-active ionic liquids concentration, structure and properties on the reaction rate of a nucleophilic substitution reaction have been investigated. Palladium catalysed reactions: besides providing a suitable reaction environment, aqueous-ionic liquid micellar media can play an active role in catalyst stabilization and speciation. Catalytic water splitting: surface-active ionic liquids can be used to design catalysts for oxygen production via catalytic water splitting and simultaneously act as reaction media.