The vast majority of Indonesia's population is Muslim, over 80% according to surveys. Indonesia is thus the world's largest Muslim-majority country by number of believers.

Once, much of Indonesia was of Buddhist or Hindu faith. Islam then spread gradually. It first appeared on Sumatra before expanding rapidly to other Indonesian islands and regions.

The Hindu princes of the time saw great interest in converting, particularly to integrate more easily into the trade networks of Muslim merchants. During this period, these merchants controlled maritime commerce. They would transit through the Strait of Malacca and use the Silk Road.

Islam today: Indonesia's leading religion

Most Indonesian Muslims practice customs that are quite liberal, sometimes influenced by Buddhist and Hindu traditions. Generally they practice Islam in a very moderate manner. Some regions have more traditional Muslims such as in Aceh, in West Java; in some Nusa Tenggara islands and in Southeast Kalimantan.

Despite a Muslim majority, the country does not apply Islamic law or Sharia as this would create a government in disagreement with the principles of Pancasila that advocate tolerance and religious freedom in Indonesia. Indeed, since 1945, the State has used these principles as a social tool aimed at unifying the different ethnic groups that make up Indonesia.

Today, many Muslims wish to maintain a pluralist State open to different religions. Indonesia is often considered a political and religious model to follow in terms of tolerance, particularly when comparing its system to that of Islamic states.