Sarna santhal or Sarna is a sacred grove in the Chota Nagpur Plateau region in which the native Sadan and tribal worship a village deity in the states of Jharkhand, Odisha, Assam, Nepal, Bangladesh, Chhattisgarh, Bihar and West Bengal. Followers of these rituals primarily belong to the Baiga, Kudumi Mahato, Ho, Kurukh, Munda and Santal. According to local belief, Gram deoti resides on the sacred grove Sarna, where sacrifice is offered twice a year. In recent years many tribal and Kudumi Mahato organization are demanding religious code for Sarna as Sarnaism, separate from Hinduism, as many tribals and kudumi mahato believe that they are nature worshipers.
Adherents of Sarnaism believe in, worship and revere a village deity as protector of village, who is called as gaon khunt/Gramadevata, Dharmes, Marang Buru, Singbonga or by other names by different tribes. Adherents also believe in, worship and revere Dharti ayo or Chalapachho Devi, the mother goddess, identified as the earth or nature.
Sarna is place of worship which is sacred grove. It is also called "gram than", Jaher than or Jaher gar, and can be found in villages. Sal trees is the sacred grove. The ceremonies are performed by the whole village community at a public gathering with the active participation of village priests, pahan. The chief assistant of village priest is called Naike.
According to the Census of India 2001, as many as 45.1 per cent of the tribal population follow other religions and persuations.