The Ambubachi Mela of Assam is an annual Hindu mela that is held at Kamakhya Temple in Guwahati, Assam. This yearly mela is celebrated during the monsoon season that falls in the Assamese month Ahaar, which is around the middle of June. It is the celebration of the yearly menstruation course of the Goddess Kamakhya. It is believed that the presiding goddess of the temple, Devi Kamakhya, also known as Mother Shakti, goes through her annual cycle of menstruation in this stretch of time. It is also believed that during the monsoon rains, the creative and nurturing power of the 'menses' of Mother Earth becomes accessible to devotees at this site during the Ambubachi mela. There is no idol of the presiding deity, however, she is worshipped in the form of a yoni-like stone instead over which a natural spring flows.

The Ambubachi mela is also known as Ameti or Tantric fertility festival since it is closely associated with the Tantric Shakti cult that is prevalent in the eastern parts of India. Some Tantric Babas make public appearances only during these four days. They remain in seclusion the rest of the year.