The Bali Aga, Baliaga, or Bali Mula, are the indigenous people of Bali. Linguistically they are an Austronesian people. Bali Aga people are predominantly located in the eastern part of the island, in Bangli especially the mountains Kintamani, East Buleleng, East Karangasem, but they can also be found in north-western and central regions. The term Bali Aga or Bali Pegunungan (Mountain Balinese) is regarded as an insult with an additional meaning of "the mountain people that are fools"; therefore, they prefer the term Bali Mula (lit. 'Original Balinese') instead.

Bali Aga people who are referred to as Bali Pegunungan (Mountain Balinese) are those that are located at Trunyan village. For the Trunyan Bali Aga people, the term Bali Aga or Bali Pegunungan (Balinese: Mountain Balinese) is regarded as an insult with an additional meaning of "the mountain people that are fools"; therefore, they prefer the term Bali Mula (lit Original Balinese) instead.

The Bali Aga/Bali Mula still maintain their old beliefs called folk Hinduism which has slight differences with Hinduism of the Balinese people one of them is not performing Ngaben cremation what most Balinese people do is to burn the bodies of people who have died, on the other hand, the Bali Aga/Bali Mula people leave the bodies lying on the ground on a tree which they call Taru Menyan until the corpse becomes only bones, the Bali Aga/Bali Mula people believe that the corpses do not smell bad because they are placed around the Taru Menyan tree, This is one of the traditions of the Bali Aga/Bali Mula community in Trunyan village and has become a unique phenomenon.

The original inhabitants of Bali are said to have come from Bedulu village long before the Hindu-Javanese immigration wave. Legend states that in Bedulu lived the last king of Pejeng (an old Balinese kingdom), Sri Aji Asura Bumibanten, who had supernatural powers. He could cut off his head without feeling pain and put it back on again. One day, his head accidentally fell into a river and was swept away. In panic, One of his servants quickly decapitated a pig and replaced the king's head with the animal's head. Embarrassed, the king hid in a tall tower, denying any visitors. A small child discovered the secret and since then, the king has become known as Dalem Bedulu, or He-who-changed-head. Another explanation is that the name comes from Badahulu or "the village upstream". After the Pejeng kingdom, the Majapahit Empire rose to power. In the year 1344, Bali Aga people under Ki Kayuselem revolted against Majapahit

An inventory of Bali Aga villages by the Public Works Office en 1988-1989 recorded about 38 traditional villages, in seven regencies. However, a research published in 2015 found 62 Bali Aga villages spread across seven regencies.

Among these seven regencies, Bangli Regency has the highest number of Bali Aga villages: 25 villages - including six in Bangli, Susut and Tembuku sub-districts. The Kintamani sub-district includes about 19 Bali Aga villages, disseminated at the foot of mount Batur, along lake Batur and in the valleys.

The Bali Aga live in isolated areas in the mountains. Compared to the lowland Balinese, their relative isolation preserved some original Austronesian elements, apparent in Bali Aga architecture. Tourists wishing to visit certain villages must be careful due to the area's geography. While visiting, it is also important to be respectful and quietly observe the preserved way of life the Bali Aga have.

In Tenganan, where tourism is more easily embraced and the people are said to be more friendly, a three-day festival called Udaba Sambah is held during June or July. Tenganan prohibits divorce and polygamy, unlike other villages.