Magnesium Chloride is the name for the chemical compounds with the formulas MgCl2 and its various hydrates MgCl2(H2O)x. These salts are typical ionic halides, being highly soluble in water. The hydrated Magnesium Chloride can be extracted from brine or sea water. Magnesium Chloride as the natural mineral bischofite is also extracted (solution mining) out of ancient seabeds. Anhydrous Magnesium Chloride is the principal precursor to magnesium metal, which is produced on a large scale. Hydrated Magnesium Chloride is the form usually used in prescription oral magnesium supplements.

Magnesium Chloride is used for a variety of other applications besides the production of magnesium: the manufacture of textiles, paper, fireproofing agents, cements and refrigeration brine, and dust and erosion control. Mixed with hydrated Magnesium Oxide, magnesium chloride forms a hard material called Sorel cement.

Magnesium Chloride is also used in several medical and topical (skin related) applications. It has been used in pills as supplemental sources of magnesium, where it serves as a soluble compound. It can also be used as an effective anaesthetic for cephalopods, some species of crustaceans, and several species of bivalve, including oysters.

For culinary uses, Magnesium Chloride is an important coagulant used in the preparation of tofu from soy milk. It is also an ingredient in baby formula milk.

Dust and erosion control uses, road departments and private industry may apply liquid or powdered Magnesium Chloride to control dust and erosion on unimproved (dirt or gravel) roads and dusty job sites such as quarries. Its hygroscopy makes it absorb moisture from the air, controlling the number of small particles which become airborne.

For chemical uses, Magnesium Chloride has shown promise as a storage material for hydrogen. Ammonia, which is rich in hydrogen atoms, is used as an intermediate storage material. Ammonia can be effectively adsorbed onto solid Magnesium Chlorid.