In past 5 years since the last report on inventorisation of STPs was released in 2015, substantial sewage treatment capacities have been added. However, still a vast gap remains in sewage generation and treatment capacities. Through this report on "National Inventory of Sewage Treatment Plants in India - 2021", attempts have been made to analyse the quantum of sewage generated, treatment capacity, sewage actually treated and treatment capacity complying to discharge norms in various States/Union Territories. This report has been prepared based on the data provide by State Pollution Control Boards (SPCBs)/ Pollution Control Committees (PCCs) and Local Bodies (LBs). The focus of the report is to analyse the time-series trends of generation of sewage and practices being adopted by the states for sewage disposal. The report evaluates the current practices prevalent in the country including technological options of sewage management.