Ambubachi Mela is the most important festival of Kamakhya temple of Guwahati and is held every year during monsoon (mid-June). It is a ritual of austerities celebrated with 'Tantric rites'. It is a common belief that the reigning diety, 'Kamakhya' , 'The Mother Shakti' goes through her annual cycle of menstruation during this period.

During Ambubashi the doors of the temple remain closed for three days. It is believed that the earth becomes impure for three days. During this time no farming work is undertaken. Daily worship and other religious performances are suspended during this period. After three days, the temple doors are reopened after the Goddess is bathed and other rituals performed. It is believed that the mother earth regains her purity now. This is purely a ritual of Tantric cult.

Ambubachi mela is held at the Kamakhya temple, after being closed for the afore-mentioned three days. On the fourth day only the devotees are allowed to enter inside the temple for worship. Thousands of devotees from all over India visit this mela.