Herein, we report the sunlight driven photocatalytic degradation of toxic organic dye, Rhodamine B using α-Bi2O3 nanosheets as an effective photocatalyst. The α-Bi2O3 nanosheets were prepared by simple annealing assisted thermal decomposition method and characterized by several techniques in order to understand its morphological, compositional, structural and optical properties. Morphological, structural and compositional investigations confirmed the formation of sheet-like morphologies, high-crystalline monoclinic crystal structure, and pure α-Bi2O3, respectively. The synthesized α-Bi2O3 nanosheets exhibited a high photocatalytic degradation of a toxic organic dye, i.e. Rhodamine B (RhB). Under optimal reaction conditions, ∼95% photocatalytic degradation of RhB (10 mg/L, pH 10) was observed in 180 min using 0.75 g/L catalyst dosage under sunlight irradiation. According to the findings, the synthesized catalyst had outstanding photocatalytic properties and can be used to cleanse textile wastewater under direct sunlight.