In the present book an attempt has been made to give an introduction to decolourization of textile dye effluent by various species of fungi. Fungi with the help of various enzymes are able to degrade and decolorize the effluent that is xenobiotic in nature. Bioreactor study is proving the efficacy of the study that gives complete degradation of xenobiotic compounds of effluent proving a great step that encouraging the revolutionary movement against water pollution.