Cobalt doped neutralized red mud (Co/NRM) nanocomposite materials were prepared by impregnation method for the photodegradation of methylene blue dye under solar light irradiation. Different Co/NRM catalysts were prepared by varying the weight ratio of Co and NRM and characterized by different instrumental techniques. Under solar light 97.21% degradation was observed in the presence of 0.08 g of Co/NRM (Co:NRM::20:80) photocatalyst within 150 min for 20 mg/L methylene blue solution at pH 9. These results underline the potential use of effective, low-cost and easily available photocatalysts for the promotion of water splitting and environmental remediation under natural sunlight.