Magnesium sulfate (MgSO₄) is an inorganic salt containing magnesium, sulfur, and oxygen. It commonly exists in various hydrated forms, with magnesium sulfate heptahydrate (MgSO₄·7H₂O), also known as Epsom salt, being the most well-known. Other hydrates, such as the monohydrate (MgSO₄·H₂O) and anhydrous magnesium sulfate (MgSO₄), also exist.