Sri Lanka's population practices a variety of religions. As of the 2011 census 70.19% of Sri Lankans were Theravada Buddhists, 12.6% were Hindus, 9.7% were Muslims (mainly Sunni) and 7.4% Christians (6.1% Roman Catholic and 1.3% other Christian). In 2008 Sri Lanka was the third most religious country in the world according to a Gallup poll, with 99% of Sri Lankans saying religion is an important part of their daily life.
The census carried out on 2001 covered 18 districts only. The district percentages shown are from 2001 census except where the numbers are italic, which are from 1981 census. Population movements have occurred after 1981, and accurate statistics did not exist for districts which were not covered in 2001 census until the 2011 census.
Theravada Buddhism is the major religion in Sri Lanka, with about 70% of the country's population as followers. Arahath Mahinda son of Indian Buddhist emperor Ashoka, led the mission to Sri Lanka in 246 BCE where he converted the Sri Lankan king of that time Devanampiya Tissa to Buddhism. Arahath Sanghamitra, daughter of King Ashoka, brought a sapling of the Bodhi tree in Buddha Gaya to Sri Lanka. She also established the Order of Nuns in Sri Lanka. The Sapling of the Bodhi tree, known as Jaya Sri Maha Bodhi was planted in the Mahameghavana Park in Anuradhapura by the King Devanampiya Tissa.
From then on, the royal families had helped to encourage the spread of Buddhism, aiding Buddhist missionaries and building monasteries. Around 200 BCE, Buddhism became the official religion of Sri Lanka. The Sacred Tooth Relic was brought to Sri Lanka in 4th century by Prince Danta and Princess Hemamala. Sri Lanka has the longest continuous history of Buddhism of any Buddhist nation. During the periods of decline, the Sri Lankan monastic lineage was revived through contacts with Myanmar and Thailand. Later on, however, Hindu and European colonial influences contributed to the decline of Buddhism in Sri Lanka. The religion of Buddhism originally started in India, which is now the home to most of the Hinduism.
In the mid 18th century the higher ordination of Buddhist monks known as Upasampada, which was defunct at the time, was revived with the help of Siamese Buddhist monks on the initiatives taken by Weliwita Sri Saranankara Thero during the reign of king Kirti Sri Rajasinha of Kandy. By the mid-19th century, Buddhist leaders such as Migettuwatte Gunananda Thera, Hikkaduwe Sri Sumangala Thera, Colonel Henry Steel Olcott and Anagarika Dharmapala started a successful national Buddhist movement for the revival of Buddhism in Sri Lanka.
Hindus make up 12.6% of Sri Lanka's population. The origins of the religion are linked to early Tamil immigration into the island since the Chola conquests in the 10th century or even earlier with the Saivite devotional movement that swept South India.
Hinduism in Sri Lanka is largely identified with the Tamil population and is concentrated in the Northern, Eastern and Central Provinces. The population declined since the 1981 census on account of Sri Lankan Tamil immigration overseas and the repatriation of 'Indian' Tamils.
A significant Hindu religious figure in Sri Lankan modern history is Satguru Siva Yogaswami of Jaffna. One of the mystics of the 20th century, Yogaswami was the official satguru and counseling sage of Lanka's several million Tamil Hindu population. The Ramakrishna Mission is somewhat active in the Amparai and Batticaloa districts while the Saiva Siddhanta school of philosophy is prevalent in the North.
By the 6th century, Arab traders had controlled much of the trade on the Indian Ocean, including that of Sri Lanka's. Many of these traders settled down in Sri Lanka, encouraging the spread of Islam. However, when the Portuguese arrived at Sri Lanka during the 16th century, many of the Arabs' Muslim descendants were persecuted, thus forcing them to migrate to the Central Highlands and to the east coast.
In modern times, Muslims in Sri Lanka have the Muslim Religious and Cultural Affairs Department, which was established in the 1980s to prevent the continual isolation of the Muslim community from the rest of Sri Lanka. Today, about 9.7% of Sri Lankans adhere to Islam; mostly from the Moor and Malay ethnic communities on the island.
According to Christian traditions, Christianity introduced by Thomas the Apostle in Sri Lanka (as well as India) during the 1st century. After his arrival, small Christian settlements were recorded to have been established on Sri Lanka's coastline.[dubious ] However, the population of Christians in Sri Lanka didn't dramatically increase until the arrival of Portuguese missionaries during the 15th century. In the 17th century, the Dutch took over Sri Lanka and Dutch missionaries were able to convert 21% of Sri Lanka's population to Christianity by 1622.
In 1796 the Dutch were displaced by the British and in 1802 Ceylon became a Crown colony. Anglican and other Protestant missionaries arrived at Sri Lanka during the early 19th century, when the British took control of Sri Lanka from the Dutch. Under British rule missionary work was undertaken by English societies: Baptist, Wesleyan Methodist, the CMS and SPG. The Salvation Army and Jehovah's Witnesses are also present in Sri Lanka.
Even so, Christianity has heavily declined in Sri Lanka ever since the end of colonial rule. By the 1980s, the population of Christians (mostly concentrated in the northwest of Sri Lanka) reached 1,283,600, 8% of Sri Lanka's population. Of these Christians, about 88% are Roman Catholics and the rest are Anglican and Protestant.