Naga  is the Sanskrit and Pali word for a deity or class of entity or being, taking the form of a very large snake, found in Hinduism and Buddhism. The use of the term naga is often ambiguous, as the word may also refer, in similar contexts, to one of several human tribes known as or nicknamed "Nagas" to elephants; and to ordinary snakes, particularly the King Cobra and the Indian Cobra, the latter of which is still called nag in Hindi and other languages of India. A female naga is a nagi

Nagas in Buddhism
Traditions about nagas are also very common in all the Buddhist countries of Asia. In many countries, the nāga concept has been merged with local traditions of large and intelligent serpents or dragons. In Tibet, the naga was equated with the klu (pronounced lu), spirits that dwell in lakes or underground streams and guard treasure. In China, the naga was equated with the long or Chinese dragon.

The Buddhist naga generally has the form of a large cobra-like snake, usually with a single head but sometimes with many. At least some of the nagas are capable of using magic powers to transform themselves into a human semblance. In Buddhist painting, the naga is sometimes portrayed as a human being with a snake or dragon extending over his head. One naga, in human form, attempted to become a monk, when telling it that such ordination was impossible, the Buddha told it how to ensure that it would be reborn a man, able to become a monk.

Nagas are believed to both live on Mount Sumeru, among the other minor deities, and in various parts of the human-inhabited earth. Some of them are water-dwellers, living in rivers or the ocean; others are earth-dwellers, living in underground caverns. Some of them sleep on top of anthills. Their food includes frogs and they love milk.

The nagas are the servants of Virupakkha, one of the Four Heavenly Kings who guards the western direction. They act as a guard upon Mount Sumeru, protecting the devas of Trāyastrimsa from attack by the Asuras.

Among the notable nagas of Buddhist tradition is Mucalinda, protector of the Buddha. In the Vajrayana and Mahasiddha Traditions according to Beer (1999), many notable fully-enlightened naga also transmitted and or transported terma into and out of the human realm that had been elementally encoded by adepts.

Muccalinda Sutta

Translated from Pali by John D. Ireland

Thus have I heard. At one time the Lord was staying at Uruvela beside the river Nerańjara at the foot of the Mucalinda Tree, having just realized full enlightenment.

At that time the Lord sat cross-legged for seven days experiencing the bliss of liberation. Now it happened that there occurred, out of season, a great rainstorm and for seven days there were rain clouds, cold winds, and unsettled weather. Then Mucalinda the naga-king left his dwelling place and having encircled the Lord's body seven times with his coils, he stood with his great hood spread over the Lord's head (thinking) to protect the Lord from cold and heat, from gadflies, mosquitoes, wind, sun, and the touch of creeping things.

At the end of those seven days the Lord emerged from that concentration. Then Mucalinda the naga-king, seeing that the sky had cleared and the rain clouds had gone, removed his coils from the Lord's body. Changing his own appearance and assuming the appearance of a youth, he stood in front of the Lord with his hands folded together venerating him.

Then, on realizing its significance, the Lord uttered on that occasion this inspired utterance:

Blissful is detachment for one who is content,
For one who has learned Dhamma and who sees;
Blissful is non-affliction in the world,
Restraint towards living creatures;

Blissful is passionlessness in the world,
The overcoming of sensual desires;
But the abolition of the conceit "I am" —
That is truly the supreme bliss.

The Naga or serpent are found in both Hindu and Buddhist mythology. They are also prominently featured in Khmer art.

The underwater kingdoms of the Naga extend across all of the world's rivers, lakes, and seas. In addition to being the keeper of the force of life stored in the waters, the Naga is also guardian of corals, shells and pearls and carries one in its head.

The early settlers of the Mekong River basin believed that the King of the Nagas is the God of an underwater kingdom called "Muang Badan". A god with almighty powers who watches over the people living in the Mekong basin.

According to ancient folklore told through the centuries, the underwater city of Muang Badan stretches beyond the Mekong itself and covers the entire subterranean realm beneath Nong Khai province, with its the capital city located near present-day Kaeng Aa-Hong, Amphoe Bueng Khan district, the deepest point in the Mekong River.

So entrenched is this ancient belief in the communities bordering the Mekong River that the eternal bond between the peoples of I-San or Northeastern Thailand and the mythical Naga is ever present in the fabric of the local culture, traditions and way of life. The tradition of floating illuminated boats on the Mekong River is one such act of worshipping the King of Nagas.

The Naga design element is incorporated into the architectural style, and depicted as motifs on structures such as temples, the palaces and stone sanctuaries of the divine kings, traditional textiles as well as the range of modern buildings such as hotels, offices, and schools.

The sinuous form of the Naga is also featured as arches around pediments, the balustrades around ponds and flanking causeways referred to as the "Naga bridge". In all of these cases, the elongated body of the Naga is symbolic of the rainbow that links the human and divine worlds.

BUDDHIST TALES OF THE NAGA
 
Naga, the Serpent King. is also mentioned in Buddhist folklore.

As the Lord Buddha went about his quest preaching to his disciples and devout followers, Naga, the serpent king watched in fascination and soon aspired to be one of the disciples of the Lord Buddha.

Endowed with powers to assume various forms, the Naga transformed itself into a human form and mingled in the midst of the disciples, listening to the sermons. However, when the Naga drifted off to sleep, the spell that was cast wore off and the impostor was exposed. With this revelation, the Lord Buddha told the Naga that as a beast, and not an earthling, it could not be ordained into monkhood and was forbidden from entering temples.
 
Hence in Buddhist temple architecture, the Naga is either depicted coiled around the outer walls of the temple or along the stairs leading to the entrance to the temple.
However, the Lord Buddha had elicited such devotion from the Naga that in spite of the ban from monkhood, Naga continued to keep its vigil over the Lord Buddha, protecting him from harm.

The statue of the Lord Buddha seated on the body of a coiled serpent and sheltered from the rain by the seven hoods of the Naga commonly featured in the Buddhist sculptures of Northeastern Thailand is one of the most significant postures.

It is said that while Lord Buddha was meditating, Mara, the Evil One sought to distract his concentration by invoking a storm. Muchalinda, the Serpent King, emerged from the roots of the tree where Lord Buddha was seated to offer protection from the rains and floods.

Nagas in Cambodia
 
In a Cambodian legend, the naga were a reptilian race of beings who possessed a large empire or kingdom in the Pacific Ocean region. The Naga King's daughter married an Indian Brahmana named Kaundinya, and from their union sprang the Cambodian people. This is why, still, today, Cambodians say that they are "Born from the Naga".

The Seven-Headed Naga serpents depicted as statues on Cambodian temples, such as Angkor Wat, apparently represent the seven races within Naga society, which has a mythological, or symbolic, association with "the seven colors of the rainbow". Furthermore, Cambodian Naga possess numerological symbolism in the number of their heads. Odd-headed Naga symbolise the Male Energy, Infinity, Timelessness, and Immortality. This is because, numerologically, all odd numbers come from One (1). Even-headed Naga are said to be "Female, representing Physicality, Mortality, Temporality, and the Earth."

Cambodians trace their ancestry back to a Brahman prince named Kaundiya, he was from a powerful kingdom in Takkisila  (north-west India), unable to inherit because he was the second son. He consulted an astrologer who advised him to get the sacred javelin from the temple of Drona (Hindu god) and seek his fortune at sea.

The prince and his crew traveled for several months and were lost in a powerful storm, when it finally cleared up, Kaundiya by now desperate for food and water made a promise to settle to wherever his javelin landed. The spear hit an island which was ruled by a powerful Naga king, a seven-headed sea serpent. Luckily at the time, the king was not present on the island, his daughter, the princess Soma tried to defend her home from Kaundiya and his men. She lost and surrended to him, the prince fell in love with the princess and married her.

The Naga king, then drank all the water surrounding the island, land emerged and presented this new kingdom to the couple as his wedding present. It is there that Kaundiya and Soma settled and founded the line of kings in Cambodia.

In Vietnam, the dragon (Vietnamese: rong or long) is the most important and sacred symbol. Similar to other dragons in Asia, it was strongly influenced by the Chinese dragon. According to the ancient creation myth of the Vietnamese people, all Vietnamese people are descended from a dragon.

To Vietnamese people, the dragon brings rain, essential for agriculture. It represents the King, the prosperity and power of the nation. Like the Chinese dragon, the Vietnamese dragon is the symbol of yang, representing the universe, life, existence, and growth.

The Legend of the 5th-generation grandson of Shennong, Lac Long Quan, in dragonkind, king of Dong sea, married a fairy, Au Co, in birdkind, daughter of king De Lai. Au Co bore 100 eggs, which hatched into 100 sons. The first-born son became the king of Lac Viet, the first dynasty of Vietnam, proclaimed himself Emperor Hung Vuong The First (who was then followed by Hung Vuong The Second, Hung Vuong The Third and so on, through 18 reigns). This is the origin of the Vietnamese proverb: "Con Rong, chau Tien" ("Children of Dragon, Grandchildren of Fairy").