Peroxynitrite (ONOO(-)) and hypochlorous acid (HOCl) are two highly reactive oxygen species generated in biological systems. The overproduction of peroxynitrite or hypochlorous acid is implicated in a broad array of human pathologies including vascular, immunological, and neurodegenerative diseases. However, unambiguous detection of these reactive oxygen species has been relatively difficult due to their short biological half-lives and multiple reaction pathways. Based on their specific chemical reactions, we have developed fluorescent probes HKGreen-1 and HKOCl-1 for highly sensitive detection of peroxynitrite and hypochlorous acid, respectively. Both probes have been demonstrated to be able to discriminate corresponding reactive species from other reactive oxygen and nitrogen species (ROS and RNS) in not only chemical systems but also biological systems. The endogenous production of peroxynitrite in neuronal cells under oxygen-glucose deprivation (OGD) conditions has been visualized for the first time by utilizing HKGreen-1 probe, whilst the endogenous production of hypochlorous acid in macrophage cells upon stimulation with LPS, IFN-gamma, and PMA has been imaged by utilizing HKOCl-1 probe.