The Molten salts having melting points near to or less than room temperature is termed ionic liquids (ILs). A full IL unit generally comprises two oppositely charged ions with a remarkable size difference, i.e., bulky cation and comparatively small anion. The ILs are also labelled as future solvents due to their design flexibility and greener approach. Owing to their large number of favourable characteristics, such as less toxicity, good solvating capacity, high conductivity, nonvolatility, super sensitivity, selectivity and electrochemical stability, these ILs have provided a broader range of applicability in the field of sensing. ILs are proven to be of good use in the area of sensors as well as biosensors, i.e., optical sensing, thermometric sensing, electrochemical sensing and fluorescent sensing, etc. The ILs can be tailored by changing cations and anions as per the demand of the applications. In the present chapter, various aspects of ILs, including the use of these ILs in various sensing applications, have been explored and summed up to present an organized view for the researcher community as well as general readers.