Indonesians (Indonesian: Orang Indonesia) are citizens or people who are identified with the country of Indonesia, regardless of their ethnic or religious background. There are more than 1,300 ethnicities in Indonesia, making it a multicultural archipelagic country with a diversity of languages, culture and religious beliefs. The population of Indonesia according to the 2020 national census was 270.2 million. 56% live on the island of Java, the world's most populous island. Around 95% of Indonesians are Native Indonesians (formerly grouped as "Pribumi"), primarily of Austronesian and Melanesian descent, with 40% Javanese and 15% Sundanese forming the majority, while the other 5% are Indonesians with ancestry from foreign origin, such as Arab Indonesians, Chinese Indonesians, Indian Indonesians, and Indos.

As of 2020, Indonesians make up 3.4% of the world's total population and Indonesia is the fourth most populous country after China, India and the United States.

Despite a fairly effective family planning program that has been in place since the 1967, for the decade ending in 2020, Indonesia's population growth was 1.1 percent. At that rate, Indonesia's population is projected to surpass the present population of the United States and would - if the current US population did not rise – become the world's third biggest after China and India by 2043. The family planning already revitalised based on the 1967 program to avoid Indonesia becoming the world's third most populous country.

With a population of 151.6 million, Java is home to 56 per cent of the Indonesian population, and is the most populous island on Earth. The Indonesian capital city, Jakarta, is located on western Java. Much of Indonesian history took place on Java. It was the centre of powerful Hindu-Buddhist empires, the Islamic sultanates and the core of the colonial Dutch East Indies. Java was also the centre of the Indonesian struggle for independence during the 1930s and 1940s. Java dominates Indonesia politically, economically and culturally.

The other major islands of Indonesia are Sumatra, Kalimantan, Sulawesi and New Guinea, which are home to the other 49 percent of Indonesian population. There are also other small populated island(s) such as Bali, Bangka, Madura, Nias, Maluku, Lesser Sunda Islands, Riau Islands and others.

There are over 1,300 ethnic groups in Indonesia. This number makes Indonesia one of the most diverse countries in the world. 95% of those are of Native Indonesian ancestry.

The largest ethnic group in Indonesia is the Javanese who make up nearly 40% of the total population. The Javanese are concentrated on the island of Java but millions have migrated to other islands throughout the archipelago because of the transmigration program. The Sundanese people 15% of the population in Indonesia, are an ethnic group that shares territory with the Javanese in that, most of the Sundanese live in the western region of Java. Malays, Batak, Madurese, Betawi, and Minangkabau are the next largest groups in the country. Many ethnic groups, particularly in Kalimantan and Papua, have only hundreds of members. Most of the local languages belong to Austronesian language family, although a significant number, particularly in Maluku Islands and Western New Guinea belong to Papuan languages. The Chinese Indonesians (Tionghoa) population makes up a little less than 1% of the total Indonesian population according to the 2000 census. Some of these Indonesians of Chinese descent speak various Chinese languages, most notably Hokkien and Hakka.

The classification of ethnic groups in Indonesia is not rigid and in some cases unclear due to migrations, cultural and linguistic influences; for example, some may consider Osing people and Cirebonese to be members of Javanese people, however, some others argue that they are different ethnic groups altogether since they have their own distinct dialects. This is the same case with Baduy people that actually are sub-ethnic of the Sundanese people but sometimes considered as separated ethnicities. An example of hybrid ethnicity is the Betawi people, descended not only from marriages between different peoples in Indonesia but also with foreign origin like Arab, Chinese and Indian migrants since the era of colonial Batavia (Jakarta).