Manasa (Sanskrit: मनसा, romanized: Manasā) is a Hindu goddess of snakes. She is worshipped mainly in Bihar, Odisha, Bengal, Andhra Pradesh, Chhattisgarh, Jharkhand, Uttarakhand, Uttar Pradesh, Haryana, Punjab, Rajasthan, Assam and other parts of northeastern India, chiefly for the prevention and cure of snakebite, and also for fertility and prosperity. In Hindu texts, Manasa is the daughter of sage Kashyapa, sister of Vasuki—king of Nāgas (serpents)—and wife of sage Jaratkaru. She is the mother of the sage Astika.

In regional tradition, her stories emphasise her bad temper and unhappiness, due to rejection by her father, Shiva, and her husband (Jaratkaru), and the hate of her stepmother Chandi (Shiva's wife, identified with Parvati in this context). Manasa is depicted as kind to her devotees, but harsh toward people who refuse to worship her. Denied full godhood due to her mixed parentage, Manasa's aim was to fully establish her authority as a goddess, and to acquire steadfast human devotees.

In the epic Mahabharata where Manasa is referred in passing mention, she is known as Jaratkaru. Her most popular name Manasa (lit. "mind-borne") originates from the Puranas, where she is the mind-borne daughter of the sage Kashyapa. She is also known as Padmavati in the Mangalkavyas of Bengal and Padmapurana of Assam, where the seed of Shiva from the earth reaches the subterranean land of the serpents via the stalk of a lotus (padma). Her epithets also include Vishahari (Bishohori, the destroyer of poison), Ayonisambhava (one not born of a woman) and Nityā (eternal). Manasa is known by various regional names - Nagmati (Goddess of snakes) in Bihar, Mare (the goddess of disease) and Barmati in Assam.

Bhattacharya and Sen suggest that Manasa originated in South India as a non-Vedic and non-Aryan goddess and is related to the Kannada folk snake-goddess Manchamma. Manasa was originally an Adivasi (tribal) goddess. She was accepted in the pantheon worshipped by Hindu groups. Later, Dimock suggests that although snake worship is found in the Vedas (the earliest Hindu scriptures), Manasa - a human goddess of snakes - has "little basis" in early Hinduism. Bhattacharya suggests another influence on Manasa being the poison-curing Mahayana Buddhist goddess, Janguli. Janguli shares her swan vehicle and her "poison-destroyer" epithet with Manasa. A theory suggests that Janguli may have been influenced by the Kirata-giri ("the conqueror of all poisons") of the Atharvaveda. According to McDaniel, she was included in the higher-caste Hindu pantheon, where she is now regarded as a Hindu goddess rather than a tribal one.

According to Tate, Manasa as Jaratkaru was initially recognized as a daughter of the sage Kashyapa and Kadru, the mother of all nagas in the epic Mahabharata. According to Bhattacharya, the Jaratkaru of the Mahabharata is not the Manasa popular in Bengal.

By the 14th century, Manasa was identified as the goddess of fertility and marriage rites and was assimilated into the Shaiva pantheon, related to the god Shiva. Myths glorified her by describing that she saved Shiva after he drank the poison, and venerated her as the "remover of poison". Her popularity grew and spread to southern India, and the cult of her followers began to rival the earliest Shaivism (the cult of Shiva). As a consequence, stories attributing Manasa's birth to Shiva emerged and ultimately Shaivism adopted this indigenous goddess into the Brahmanical tradition of mainstream Hinduism. Alternatively, Vasudev suggests that the Bengali tale of Manasa reflects rivalry between Shaivism and the goddess-centric Shaktism.

Manasa is depicted as a beautiful woman with a golden complexion (hence the nickname Gauri, Golden) and smiling face. She wears red garments and gold jewellery. She has four arms, with her upper right hand holding a shankh (conch) and her left hand holding her favorite flower - a lotus. Her lower left hand holds a snake and the right lower right hand displays Abhayamudra (gesture of fearlessness). She is covered with snakes, sitting on a lotus platform (thus known by her epithet Padmalaya) or standing upon a snake. She is sheltered by the canopy of the hoods of seven cobras. Sometimes, she is depicted with a child (assumed to be her son, Astika) on her lap. Her vahana (mount) is a swan. She is also accompanied by Neta (Neto), her female companion.

In Bengal, she is rarely seen with her husband, Jaratkaru. In some of her idols she is shown with Behula and Lakshminder.