The encyclopedia consists 13 subareas as follows: 1: Synthesis and Characterisation of Ionic Liquids (Section Editors: Prof. Fu-Wei Li and Prof. Zhen Li) 2: Physicochemical Properties of Ionic Liquids (Section Editors: Asso. Prof. Qing Zhou, Prof. Xingmei Lu and Prof. Xiaoyan Ji) 3: Computational and Theoretical Modeling of Ionic Liquids (Section Editors: Prof. Guang Feng and Prof. Peter T. Cummings) 4: Toxicology and Biodegradation of Ionic Liquids (Section Editors: Prof. Chunxi Li and Prof. Stefan Stolte) 5: Ionic Liquids in Electrochemistry (Section Editors: Prof. Yingying Lu, Prof. Houlong Zhuang and Prof. Chuan Zhao) 6. Ionic Liquids in Organic Reaction (Section Editors: Prof. Liang-Nian He and Prof. Bhalchandra M. Bhanage) 7. Ionic Liquids in Separation (Section Editors: Prof. Huabin Xing) 8. Ionic Liquids in Biomass and Biomolecules (Section Editors: Prof. Toshiyuki Itoh and Prof. Jian Sun) 9. Ionic Liquids in Materials Science (Section Editors: Prof. Sheng Dai and Prof. Tao Wang) 10. Ionic Liquids in Polymer Science (Section Editors: Asso. Prof. Jinming Zhang and Prof. Jun Zhang) 11. Ionic Liquids in Environmental Science (Section Editors: Prof. Tiancheng Mu, Prof. Arunprakash T. Karunanithi and Prof. Yingxiong Wang) 12. Ionic Liquids in Green Chemistry (Section Editors: Prof. Buxing Han and Prof. Peter Licence) 13. Emerging Applications of Ionic Liquids (Pharmacology, Food Science, Agriculture, Nuclear Science Technology, Optics) (Section Editors: Prof. Zhonghao Li and Prof. Maya Guncheva) This encyclopedia is systematic and comprehensive, with detailed descriptions about theory, technology, and industrial applications. This encyclopedia is valuable for students, researchers and industrial players, giving them a quick understanding and overview of ionic liquids in various aspects.