A novel near-infrared (NIR), turn-on fluorescence probe containing a phosphinate group as a recognizing moiety for the selective detection of O2˙(-) with a low limit of detection (LOD, 9.9 nM) was developed. has good cell-membrane permeability, intracellular stability, and low cytotoxicity. In addition, we successfully applied the to visualize O2˙(-) in live zebrafish, mouse and, for the first time, in mouse liver.