Chloride,is a chemical compound containing chlorine. Most chlorides are salts that are formed either by direct union of chlorine with a metal or by reaction of hydrochloric acid with a metal, a metal oxide, or an inorganic base. Chloride salts include, Nacl, KCL, Cacl₂, and NH₄cl. Most chloride salts are readily soluble in water, but mercurous Chloride and Silver Chloride are insoluble, and lead chloride is only slightly soluble. Some chlorides, e.g., antimony chloride and bismuth chloride, decompose in water, forming oxychlorides.

Many metal chlorides can be melted without decomposition; two exceptions are the chlorides of gold and platinum. Most metal chlorides conduct electricity when fused or dissolved in water and can be decomposed by electrolysis to chlorine gas and the metal.

Chlorine forms compounds with the other halogens and with oxygen; when chlorine is the more electronegative element in the compound, the compound is called a chloride. Thus, compounds with bromine and iodine are bromine chloride, BrCl, and iodine chloride, ICI, but compounds with oxygen or fluorine are oxides or fluorides respectively.

Many organic compounds contain chlorine, as is indicated by common names such as carbon tetrachloride, methylene chloride, and methyl chloride.Chloride is one of the most important electrolytes in the blood.It helps keep the amount of fluid inside and outside of cells in balance. It also helps maintain proper blood volume, blood pressure, and pH of body fluids. Most of the chlorides in human body come from salt they eat.

The presence of chlorides, e.g. in seawater, significantly aggravates the conditions for pitting corrosion of most metals (including stainless steels, aluminum, aluminum alloys, and high-alloyed materials) by enhancing the formation and growth of the pits through an autocatalytic process.