Prehistoric Indonesia is a prehistoric period in the Indonesian archipelago that spanned from the Pleistocene period to about the 4th century CE when the Kutai people produced the earliest known stone inscriptions in Indonesia. Unlike the clear distinction between prehistoric and historical periods in Europe and the Middle East, the division is muddled in Indonesia. This is mostly because Indonesia's geographical conditions as a vast archipelago caused some parts — especially the interiors of distant islands — to be virtually isolated from the rest of the world. West Java and coastal Eastern Borneo, for example, began their historical periods in the early 4th century, but megalithic culture still flourished and script was unknown in the rest of Indonesia, including in Nias and Toraja. The Papuans on the Indonesian part of New Guinea island lived virtually in the Stone Age until their first contacts with modern world in the early 20th century. Even today living megalithic traditions still can be found on the island of Sumba and Nias.

Sangiran is an archaeological excavation site in Java in Indonesia. According to a UNESCO report (1995) "Sangiran is recognized by scientists to be one of the most important sites in the world for studying fossil man, ranking alongside Zhoukoudian (China), Willandra Lakes (Australia), Olduvai Gorge (Tanzania), and Sterkfontein, and more fruitful in finds than any of these."