Manasa is a Hindu goddess of snakes, worshipped mainly in Bihar, Bengal, Jharkhand, Lower Assam and other parts of northeastern India and in Uttarakhand chiefly for the prevention and cure of snakebite and also for fertility and prosperity. Manasa is the sister of Shesha and Vasuki, king of Nāgas (serpents) and wife of sage Jaratkaru. She is also the mother of the sage Astika. She is also known as Vishahari (the destroyer of poison), Nityā (eternal) and Padmavati.Generally, Manasa is worshiped without an image. A branch of a tree, an earthen pot or an earthen snake image is worshiped as the goddess,though images of Manasa are worshipped too. She is worshiped for protection from and cure of snake bites and infectious diseases like smallpox and chicken pox.
The Puranas are the first scriptures to speak about her birth. They declare that sage Kashyapa is her father, not Shiva as described in the later Mangalkavyas. Once, when serpents and reptiles had created chaos on the Earth, Kashyapa created the goddess Manasa from his mind (mana). The creator god Brahma made her the presiding deity of snakes and reptiles. Manasa gained control over the earth, by the power of mantras she chanted. Manasa then propitiated the god Shiva, who told her to please the god Krishna. Upon being pleased, Krishna granted her divine Siddhi powers and ritually worshiped her, making her an established goddess.
The goddess is widely worshiped in the rainy season, when the snakes are most active. Manasa is also a very important fertility deity, especially among the lower castes, and her blessings are invoked during marriage or for childlessness. She is usually worshiped and mentioned along with Neto, who is called Neta, Netidhopani, Netalasundori, etc. in various parts of Bengal.In North Bengal, among the Rajbanshis, Manasa is one of the most important goddesses, and her thaan (shrine) may be found in the courtyard of almost every agrarian household. Among the lower-caste Hindus of East Bengal (present-day Bangladesh)too, she is worshiped with great pomp.
Manasa is ceremonially worshiped on Nag Panchami - a festival of snake worship in the Hindu month of Shravan (July–August). Bengali women observe a fast (vrata) on this day and offer milk at snake holes.