Abstract: The present invention relates to the production of chlorine and magnesium oxide. According to the process substantially anhydrous magnesium chloride, containing at least 95% MgCl.sub.2, is admixed with particulate magnesium oxide and contacted with gas comprising oxygen at a temperature from about 700.degree. C. to about 1100.degree. C. One of the advantages of the process according to the present invention is to utilize the exothermicity of the oxidation of the molten magnesium chloride, the reaction being self-sustained. According to a preferred embodiment, the particulate magnesium oxide is preheated at a temperature of above 720.degree. C. before it is admixed with the molten magnesium chloride and serves as the heat transfer agent for the subsequent oxidation of the magnesium chloride.The process may be carried out in a stack reactor or in a fluidized bed reactor. The oxidation is effected with substantially dry, pure oxygen or air.