Kerala has welcomed newcomers from earliest times and this has resulted in many religions arriving here, finding acceptance and followers, and staying on. Sixty per cent of Kerala's population today is Hindu, 20 per cent Muslim and 20 per cent Christian. While people of different faiths are spread all over the state, a major part of the Muslim population is located towards the north and the Christians in the central part. Both these religions have been influenced to a great extent by Hinduism and local customs. It's not uncommon to see people of different faiths worshipping together on major festival days.
Hinduism, one of the oldest extant religions, evolved in Kerala from the combined religious practices of the Dravidians and the Aryan Brahmins. It is Vishnu in his form as Sri Padmanabha (padma - lotus, nabha - navel) that is most often revered here. Krishna, one of Vishnu's avatars, is a popular deity; Bhagavathy, also known as Bhadrakali, is the manifestation of the fierce and powerful goddess Kali and immense importance is given to this goddess in Kerala. Ayyappan, once a village deity, has risen in importance and is very popular now, with millions of devotees visiting his shrine in Sabarimala. Shiva the destroyer, Saraswati the goddess of learning, Parvati the divine or universal mother, Ganesh the elephant-headed god, Subramanya the god of war and Nagaraja the serpent deity are all worshipped here, along with many other gods of the Hindu pantheon.
The coming of Islam was an inevitable outcome of the ties between Kerala and the Middle East. Just 30 years after prophet Mohammed documented his revelations from Allah, one of his followers, Malik Ibn Dinar, brought the new belief to Kerala in 643 CE. Like other religions Islam found a tolerant and accepting society in Kerala, and even royal patronage, particularly from the powerful Zamorins of Kozhikode.
Legend says that the apostle St Thomas introduced Christianity to Kerala in 52 CE. He is said to have built seven churches along the coast, each associated with one of his miracles. In 345 CE a Syrian merchant called Thomas Cana (Knaithomman) who arrived at Cranganore began to preach Christianity and converted many families. The rites and practices were those of the Syrian church and Syriac the language of the services. Francis Xavier arrived in 1542 and administered to coastal Christians, mainly lower caste people who had earlier been converted by the Portuguese and who hoped inclusion in a Christian community would free them from the hardship of the rigid caste system and protect them from their Portuguese masters. The formation of the Syro-Malankara Church in 1930 enabled Syrian Christians and Latin Christians to follow their own practices. 
The exact origin of Judaism in Kerala is still a matter of debate. There are different accounts but by the 10th century CE Jews had become influential merchants and the ruler, Bhaskara Ravi Varma, granted them a series of privileges including a grant of land, the village of Anjuvannam near Kodungallur, and the revenues from it. After the community was almost totally destroyed by jealous Arab traders in the 16th century the remaining Jews fled to Cochin where they survived under the Raja's protection. In 1568 they built their synagogue which was destroyed by the Portuguese in 1662 but rebuilt two years later.
Jainism and Buddhism came to Kerala around the 3rd century BCE, and flourished till they were eventually absorbed by Hinduism. Jain sites can still be seen at Palakkad, Sulthan Bathery and Alappuzha. The Sabarimala shrine is said to have originally been Buddhist. The influence of Buddhism can be seen in literature, art, architecture and the Ayurvedic system of medicine.