Waste from various dyes as a result of industrial development is an important source of pollutants for water resources; These wastes are frequently carcinogenic, mutagenic and toxic to aquatic life, so treating wastewater is vitally important. Photocatalytic purification is a popular method because it can break down dye molecules and change them into non-toxic, small and harmless species. Moreover, utilizing the power of sunlight, this technology holds significant promise for enabling environmentally friendly, sustainable, and economically viable technologies. The non-toxic polymeric photocatalyst graphitic carbon nitride (gC3N4) is an n-type semiconductor. Its facile and economical synthesis, effective band structure, and stability make it a popular option for photocatalytic investigations. It is crucial to develop nanocomposites to boost the capacity of materials for photocatalysis. The objective of this study is to fabricate nanocomposites of graphitic carbon nitride from thiourea, incorporating varying ratios of bismuth oxide through thermal condensation. The aim is to employ these composites for the catalytic degradation of Methylene Blue (MB) and Rhodamine B (Rh B) dyes. The synthesized samples' morphological and structural characteristics were studied. Their photocatalytic activity against methylene blue and rhodamine B dyes has also been reported. The Bi2O3/gC3N4 heterostructured samples were prepared considering bismuth nitrate and thiourea at weight ratios of 0.125:10, 0.25:10, and 0.5:10. In the study, the Bi2O3/gC3N4 heterostructured sample with the lowest bismuth doping rate was seen to have the highest photocatalytic degradation efficiency. A remarkable degradation rate, reaching 98.83 % within 70 min for MB and 98.59 % within 60 min for RhB dye was observed. The enhanced photocatalytic activities of the synthesized composite can be attributed to the synergistic effect of the heterostructure developed between graphitic carbon nitride and bismuth oxide. As a result, this study has shown promise that Bi2O3/gC3N4 composite photocatalysts can be an effective material for removing dyes.