A Nagaraja (Sanskrit: नागराज nāgarāja, lit. 'king of the nagas') is a king of the various races of the nāga, the divine or semi-divine, half-human, half-serpent beings that reside in the netherworld (Patala), and can occasionally take human form. Rituals devoted to these supernatural beings have been taking place throughout South Asia for at least two thousand years.

Hindu texts refer to three main beings by this title: Shesha, Takshaka, and Vasuki. All of them are the children of the rishi Kashyapa and Kadru.

Shesha, also sometimes known as Ananta, is the eldest brother, and the first serpent king of all serpents. A devotee and a mount of Vishnu, he serves as the deity's bed and is named as the noblest of all nagas. He is the being that supports the earth, on the behest of the creator god, Brahma, obtaining the boon to stand ever firmly on the concept of dharma.

Vasuki is the second serpent king in Indian religions. He is a devotee of Shiva, who always wears the nāga around his neck.

Takshaka is the third, and the present serpent king. In the Mahabharata, he ruled the Khandava forest, which was then burnt by the Pandava Arjuna. Later, Takshaka slew Parikshit, the grandson of Arjuna.

These serpents are a group of a thousand brothers, and they also have a sister, whose name is Manasa.

A temple of the Nagaraja Vasuki is present in Gujarat's district of Thangadh.

At Nagercoil, in Kanyakumari district's of Tamil Nadu, a temple dedicated to Nagaraja exists.