1,1,2,2,3,3,4,4,4-nonafluorobutane-1-sulphonic acid is a fluorinated compound with the molecular formula C4F9O3S. It consists of a perfluoroalkyl sulfonic acid group attached to a butane chain. This chemical is known for its strong acidity and stability, making it valuable for various applications in organic synthesis, electrochemistry, and surface modifications.