Elemental chlorine is produced commercially from brines by electrolysis, primarily in the chlor-alkali process. The high oxidation potential of elemental chlorine has led to the development of commercial bleaches and disinfectants, and reagents for many processes in the chemical industry. Chlorine is used in the manufacture of a wide range of consumer products, about two-thirds of which are organic chemicals such as polyvinyl chloride (PVC), intermediates in the production of many plastics, and other end products that do not contain the element chlorine. As a commonly used disinfectant, elemental chlorine and chlorine-generating compounds are more directly used in swimming pools to maintain the sanitation of swimming pools. High concentrations of elemental chlorine are extremely dangerous and toxic to most living organisms. As a chemical warfare agent, chlorine was first used as a poison gas weapon in World War I.

In the form of chloride ion, chlorine is necessary for all known species of life. Other types of chlorine compounds are rare in living organisms, and artificially produced chlorinated organics range from inert to toxic. In the upper atmosphere, chlorinated organic molecules such as chlorofluorocarbons have been linked to ozone depletion. Oxidation of chloride ions in neutrophils produces small amounts of elemental chlorine as part of the immune system's response to bacteria.