Abstract: Superoxide ion has been generated in room temperature ionic liquid trihexyl (tetradecyl) phosphonium bis (trifluoromethylsulfonyl)imide, [P14,666][N(Tf)2]. Cyclic voltammetry and chronoamperometry techniques were used for the electrochemical generation of O·2•¯, while chemical generation was done by adding KO2 to dimethylsulphoxide (DMSO). The long term stability of O2•¯ was investigated using UV/Vis spectrophotometer. It was found that the quaternary phosphonium cation, [P14,666]+ is a reasonably stable cation in the presence of O2•¯ which indicates the possible use of these ILs for further useful applications.