Indonesia's 210 million people make it the world's fourth-most populous nation. The island of Java is one of the most densely populated areas in the world, with more than 107 million people living in an area the size of New York State. Indonesia includes numerous related but distinct cultural and linguistic groups, many of which are ethnically Malay. Since independence, Bahasa Indonesia (the national language, a form of Malay) has spread throughout the archipelago and has become the language of most written communication, education, government, and business. Many local languages are still important in many areas, however. English is the most widely spoken foreign language. Education is free and compulsory for children through grade 9. Although about 92% of eligible children are enrolled in primary school, a much smaller percentage attend full time. About 44% of secondary school-age children attend junior high school, and some others of this age group attend vocational schools.

Constitutional guarantees of religious freedom apply to the five religions recognized by the state, namely Islam (87%), Protestantism (6%), Catholicism (3%), Buddhism (2%), and Hinduism (1%). In some remote areas, animism is still practiced.