Posttranslational changes in the redox state of cysteine residues can rapidly and reversibly alter protein function, modulating biological processes and drug pharmacology. Recent innovations in organosulfur chemistry, small-molecule tools, and computational methods for proteomic analysis have dramatically improved selectivity, cellular application, and site-specific quantitation of the cysteine redoxome. In this perspective, we start with a brief overview of cysteine sulfur chemistry and factors affecting thiol reactivity, followed by a critical discussion of similarities and differences between reactive and redox-sensitive cysteine residues. Next, we address mechanisms of post-translational cysteine oxidation and methods to quantify redoxome site-stoichiometry to prioritize follow-up study. Finally, we highlight recent chemoproteomic studies of the cysteine redoxome that offer new insights into the regulation of physiological processes and provide a framework for development of novel redox-based targeted therapeutic strategies.