This study investigates the solidification/stabilization of chromium (Cr) in red mud-based geopolymers. The research focuses on incorporating up to 1.5 wt% of Cr(III) salts (CrCl$_3$ and Cr$_2$O$_3$) and Cr(VI) salts (Na$_2$CrO$_4$ and CaCr$_2$O$_7$) into the geopolymer matrix. The results show that the red mud-based geopolymer can effectively solidify/stabilize different types of Cr salts with a rate of over 99.61%. The geopolymer is environmentally safe when the dosage of CaCr$_2$O$_7$ is ≤1.0 wt%, or the dosage of CrCl$_3$, Cr$_2$O$_3$, and Na$_2$CrO$_4$ is ≤1.5 wt%. The compressive strength and durability of the Cr-containing geopolymers are influenced by the type and content of Cr salts. Freeze-thaw cycles are found to be more destructive than sulfate attack or acid rain erosion. The solidification/stabilization of Cr is attributed to chemical binding through the formation of Cr-containing hydrates and doping into N-A-S-H and C-A-S-H gel frameworks, as well as physical encapsulation by hydration products. This study provides a reference for treating hazardous Cr-containing wastes using solid waste-based geopolymers.This study investigates the solidification/stabilization of chromium (Cr) in red mud-based geopolymers. The research focuses on incorporating up to 1.5 wt% of Cr(III) salts (CrCl$_3$ and Cr$_2$O$_3$) and Cr(VI) salts (Na$_2$CrO$_4$ and CaCr$_2$O$_7$) into the geopolymer matrix. The results show that the red mud-based geopolymer can effectively solidify/stabilize different types of Cr salts with a rate of over 99.61%. The geopolymer is environmentally safe when the dosage of CaCr$_2$O$_7$ is ≤1.0 wt%, or the dosage of CrCl$_3$, Cr$_2$O$_3$, and Na$_2$CrO$_4$ is ≤1.5 wt%. The compressive strength and durability of the Cr-containing geopolymers are influenced by the type and content of Cr salts. Freeze-thaw cycles are found to be more destructive than sulfate attack or acid rain erosion. The solidification/stabilization of Cr is attributed to chemical binding through the formation of Cr-containing hydrates and doping into N-A-S-H and C-A-S-H gel frameworks, as well as physical encapsulation by hydration products. This study provides a reference for treating hazardous Cr-containing wastes using solid waste-based geopolymers.