Abstract: The invention relates to an inorganic, halogen-free flameproofing agent made of modified, rehydrated red mud (MR2S), having a mineral composition of 10 to 50 weight percent of iron compounds, 12 to 35 weight percent of aluminum compounds, 5 to 17 weight percent of silicon compounds, 2 to 21 weight percent of TiO2, and 0.5 to 6 weight percent of calcium compounds, wherein the compounds of iron have a hydroxide and oxide hydrate fraction greater than or equal to 50 weight percent, preferably greater than or equal to 80 weight percent, relative to the oxide fraction of the iron compounds, and wherein the compounds of aluminum have a hydroxide and oxide hydrate fraction greater than or equal to 50 weight percent, preferably greater than or equal to 80 weight percent, relative to the oxide fraction of the aluminum compounds. The invention further relates to a flameproofed material system comprising a flammable material and the inorganic, halogen-free flameproofing agent and to a method for the production thereof.