Bathouism (also, Bathou) is the folk religion of the Boro people of Assam in Northeast India. The name Bathou (Ba, five; thou, deep) in Boro means five principles. The five principles are: bar (air), orr (fire), ha (earth), dwi (water) and okhrang (ether). The chief deity, called Bathoubwrai (bwarai: "the Elder")— omnipresent, omniscient and omnipotent— is said to have created the five principles. Though there are other minor gods and goddesses, Bathoubwrai is considered the Supreme God. Bathoubwrai is unseen. The second most important deity is Mainao, the daughter of Bathoubwrai, who is considered as the "protector of the rice fields".

Bathouism has evolved and adapted over time, shaped by various social, cultural, and historical factors. These influences have led to the emergence of different variants within Bathouism. While the core beliefs and principles remain largely the same, certain practices and rituals have undergone changes or have been interpreted differently among various branches. One significant factor influencing Bathouism has been its interaction with other religions and belief systems, such as Hinduism.

Currently, within Bathouism, there are various branches, including Bibar Bathou, Bwli Bathou, Aroj Bathou, Moni Bathou, Jangkhrao Bathou, and Sonathon Bathou, among others.

The altars of Kamaika (Khamaikha), Mainaw and Bathou are situated in the easternmost part of the main house. Bathou is always worshiped in conjunction with the goddess Mainaw /Kamaika (Khamakha). when worshiping, Baraja remains on the right side of Bathou and Mainaw remains on the left side and the worshipers always face east. When you bow down to the lamp and incense sticks in the Bathou, you have to rotate it 5 times in the anti-clockwise direction While to the Mainaw one is to rotate it 7 times in the anti-clockwise direction.

The sijou plant, Euphorbia neriifolia is considered the living embodiment of Bathoubwrai. Families that follow Bathouism plant a sijou shrub at the northeast corner of their courtyard, in an altar called sijousali. Bodo communities that follow Bathouism generally plant a sijou shrub at a community land, fenced with eighteen pairs of bamboo strips with five fastenings. Each pair symbolizes a pair of minor god-goddess. The five fastenings signify, from bottom: birth, pain, death, marriage and peace/pleasure. The bottom three fastenings, called bando, are those that one cannot escape in life; whereas the top two one could. In the past, thulsi and jathrasi plants were also commonly used in place of the sijou plant.

Sidney Endle differentiates between household gods and community gods. Of the household gods Bathoubwrai, Mainao, Song Bwrai/Burai and Bura Bagh Raja are considered prominent. The practice of representing Bathoubwrai by the sijou tree was more common among Boros (or Mech) of Goalpara region, and less so in Darrang. Song Raja is usually represented inside the house in an altar called dham, a deity who obtains devotion from women, and receives offerings during women's menses; but these offerings are eventually brought out and laid at the sijou tree representing Bathou.

The eighteen pairs of gods-goddesses are:

Traditional Bathouism did not have any written scriptures or religious books, nor temples. Worship is performed at the sijousali, and constitutes offering animals and fowls for sacrifice and rice beer. Notable religious festivals were Kherai, Garja and others. These ceremonies are performed by priests called Douri (male priest) and Doudini (female priest). This religion was not organized.