Hinduism. with around 80% of the Indian population it's adherent. It's really not one religion as such, but has been mislabeled as so mainly to differentiate it from Islam and more prominent Sramana traditions ie. Buddhism & Jainism. read more
Today this religion is the largest growing religion in terms of voluntary conversions and 3 rd. largest in world and largest in India with close to 81% Indians practicing it. 79.08% as per 2011 census. read more