salt water, particularly a highly concentrated water solution of common salt (sodium chloride). Natural brines occur underground, in salt lakes, or as seawater and are commercially important sources of common salt and other salts, such as chlorides and sulfates of magnesium and potassium.

Brine is used as a preservative in meat-packing (as in corned beef) and pickling. In refrigeration and cooling systems, brines are used as heat-transfer media because of their low freezing temperatures or as vapour-absorption agents because of their low vapour pressure. Brine is also used to quench (cool) steel.