[6] Indonesia has a relatively young population compared to Western nations, though it is aging as the country's birth rate has slowed and its life expectancy has increased.

[1] Age structure in Indonesia (2020)[1] Population Estimates by Sex and Age Group (01.VII.2020) (Data are based on the publication: "Indonesia Population Projection 2015-2045"):[16] Source: UN DESA, World Population Prospects, 2022[17] Total Fertility Rate (TFR) (Wanted Fertility Rate) and Crude Birth Rate (CBR):[18] Total fertility rate (TFR) and population over age 60 by region as of 2010:[19] Indonesia is a country of great ethnic diversity, with approximately 600 distinct indigenous ethnic groups living side by side across more than 17,000 islands.

Another large group is the Melanesian peoples, who inhabit the eastern part of Indonesia (the Maluku Islands, Western New Guinea, and the East Nusa Tenggara) in Oceania.

[22][23][24] The Javanese are the largest ethnic group, accounting for 40.2% of the population and are culturally, economically, and politically dominant.

The Javanese are concentrated in Java, the most populous island, especially in the central and eastern parts, and also in significant numbers in most provinces due to extensive migration throughout the archipelago.

Religion in Indonesia (2023)[31][32] Indonesia is the world's most populous Muslim-majority nation; based on civil registration data in 2023 from Ministry of Home Affairs, 87.06% of Indonesians are Muslims, 10.47% Christians (7.41% Protestants, 3.06% Roman Catholic), 1.68% Hindu, 0.71% Buddhists, 0.03% Confucians and 0.05% other faiths.