In this work, and for the first time, the production of waste-based magnetic geopolymer spheres by a simple heat treatment under a reductive atmosphere is reported. Upon heat treatment, the iron oxide present in bauxite wastes (red mud), used as a solid precursor, is reduced to magnetite, thus producing magnetic spheres without the need for the addition of any secondary magnetic materials. The magnetisation of these mm-size materials reached 5.34 A m