Magnesium bromide are inorganic compounds with the chemical formula MgBr₂(H₂O)_x, where x can range from 0 to 9. They are all white deliquescent solids. Some magnesium bromides have been found naturally as rare minerals such as bischofite and carnallite.

Magnesium bromide can be synthesized by treating magnesium oxide (and related basic salts) with hydrobromic acid. It can also be made by reacting magnesium carbonate and hydrobromic acids, and collecting the solid left after evaporation.

As suggested by its easy conversion to various hydrates, anhydrous MgBr₂ is a Lewis acid. In the coordination polymer with the formula MgBr₂(dioxane)₂, Mg²⁺ adopts an octahedral geometry.

Magnesium bromide is used as a Lewis acid catalyst in some organic synthesis, e.g., in aldol reaction.

Magnesium bromide also has been used as a tranquilizer and as an anticonvulsant for treatment of nervous disorders.

Magnesium bromide modifies the catalytic properties of palladium on charcoal.

Magnesium bromide hexahydrate has properties as a flame retardant.

Treatment of magnesium bromide with chlorine gives magnesium chloride. This reaction is employed in the production of magnesium chloride from brines.