Anhydrous magnesium chloride is a chemical compound with the formula MgCl₂. It is the anhydrous, or water-free, form of magnesium chloride, which means it lacks water molecules that are often associated with hydrated forms of the compound. This substance is commonly used in various industrial applications due to its properties as a strong Lewis acid and a source of magnesium ions.

In industry, anhydrous magnesium chloride is crucial in the production of magnesium metal. It is also used as a precursor to other magnesium compounds and as a catalyst in organic synthesis. Additionally, it is employed in the preparation of fluxes for aluminum, magnesium, and other non-ferrous metals, which helps in reducing the melting points of these metals and improving their processing.

In the laboratory, anhydrous magnesium chloride is often used to dry solvents and in the synthesis of Grignard reagents, which are important in organic chemistry. It appears as a white to off-white crystalline solid that is highly hygroscopic, meaning it readily absorbs moisture from the air, and is soluble in water.