This paper evaluates India’s annual waste-to-energy potential through biomethane production, and the corresponding greenhouse gas abatement. Biodegradable wastes generated across various sectors (agriculture, horticulture, animal husbandry, municipalities, sericulture, fisheries, and industries) are examined, many of which have not been considered previously for India’s bioenergy potential assessments. The degree of replaceability of present-day unclean fuels and the net avoided greenhouse gas emissions from the utilisation of this biomethane are evaluated for three separate end use scenarios: electricity generation, cooking, and road transportation. The total biomethane generation potential is 125 billion cubic metres, after considering a gas leakage rate of 3%. The corresponding total heat and electrical energy generation potentials are 4.49 EJ and 747.62 TWh respectively; the breakdown of this for all the states and union territories of India is also calculated. Biomethane from wastes could have provided for either 47% of India’s gross generated electricity or 91% of India’s road transport fuel demand in the financial year of 2018-19. Less than 43% of this biomethane could supply the entirety of the country’s cooking fuel demand. The corresponding avoided emissions from the displacement of fossil fuels and the prevention of crop residue field burning and municipal waste dumping are between 283 and 460 million kilograms of carbon dioxide equivalents, excluding the contribution from black carbon. The avoided particulate emissions from crop residue burning prevention is around 2 million tonnes. Thus, this paper makes a strong case for biomethane generation from wastes in India to appropriately address climate change impact, pollution, and waste disposal problems, and aims to inform and influence energy policy in the country, with additional considerations of the gap between the potential and the the state-of-the-art, and the technical and socio-economic challenges of waste-to-energy schemes. In addition to the quantitative evaluations, this paper contains a comprehensive compilation of data on waste and biomethane generation potentials from experiments and surveys scattered across the literature; it is hoped that this will be a valuable resource for future research, energy assessments, and policy considerations.