Varuna (वरुण) is a Vedic (वैदिक) Deity associated initially with the sky, later also with the seas as well as Ṛta (ऋत / "order, rule, truth") and Satya (सत्य / "truth").
He is found in the oldest layer of Vedic (वैदिक) Literature of Hinduism, such as hymn 7.86 of the Rigveda (ऋग्वेद).

In the earliest layer of the Rigveda (ऋग्वेद), Varuna (वरुण) is the Guardian of Moral Law, one who punishes those who sin without remorse, and who forgives those who err with remorse.
He is mentioned in many Rigvedic (ऋग्वेदिक) Hymns, such as 7.86-88, 1.25, 2.27-30, 8.8, 9.73 and others.
His relationship with waters, rivers and oceans is mentioned in the Vedas (वेद).

Vedic (वैदिक) poets describe him as an aspect and one of the plural perspectives of the Agni (अग्नि / "Fire"), one of the Primary deity.

Varuna (वरुण) and Mitra (मित्र) are the Gods of the societal affairs, and are often twinned Mitra-Varuna.
Both Mitra (मित्र) and Varuna (वरुण) are classified as Asuras (असुर / a class of Divine beings or power-seeking Deities) in the Rigveda (ऋग्वेद) - (e.g. RV 5.63.3), although they are also addressed as Devas (वेद) as well (e.g..60.12).

Varuna (वरुण), being the King of the Asuras (असुर), was adopted or made the change to a Deva (वेद) after the structuring of the Primordial Cosmos, imposed by Indra (इन्द्र) after he defeats Virtra (वृत्र).

- In the Vedic (वैदिक) Religion, Ṛta (ऋत / "order, rule; truth") is the principle of natural order which regulates and coordinates the operation of the Universe and everything within it.
In the hymns of the Vedas (वेद), Ṛta (ऋत) is described as that which is ultimately responsible for the proper functioning of the natural, moral and sacrificial orders.
Conceptually, it is closely allied to the injunctions and ordinances thought to uphold it, collectively referred to as Dharma (धर्म), and the action of the individual in relation to those ordinances, referred to as Karma (कर्म) - two terms which eventually eclipsed Ṛta (ऋत) in importance as signifying natural, religious and moral order in later Hinduism.
- Satya (सत्य) is the Sanskrit (संस्कृत) word for truth.
It also refers to a virtue in Indian Religions, referring to being truthful in one's thought, speech and action.
In Yoga (योग), Satya (सत्य) is one of five Yamas (यम / "reining in" or "control"), the virtuous restraint from falsehood and distortion of reality in one's expressions and actions.
- The Rigveda (ऋग्वेद) is an Ancient Indian collection of Vedic Sanskrit Hymns (वैदिक संस्कृत भजन) along with associated commentaries on liturgy, ritual and mystical exegesis.
It is one of the four sacred canonical texts (श्रुति, Śruti) of Hinduism known as the Vedas (वेद).
- The Vedas (वेद / "Knowledge") are a large body of religious texts originating in Ancient India.
Composed in Vedic Sanskrit (वैदिक संस्कृत), the texts constitute the oldest layer of Sanskrit (संस्कृत) Literature and the oldest scriptures of Hinduism.
Hindus consider the Vedas to be apauruṣeya (अपौरुषेय), which means "not of a man, superhuman" and "impersonal, authorless".

Rama (राम) interacts with Varuna (वरुण) in the Hindu epic Ramayana (रामायणम्, Rāmāyaṇam).
- Rama (राम) also known as Ramachandra (रामचंद्र), is a major Deity of Hinduism.
He is the seventh avatar (अवतार / "descent" / the material appearance or incarnation of a Deity on Earth) of the God Vishnu (विष्णु), one of his most popular incarnations along with Krishna (कृष्ण) and Gautama Buddha (सिद्धार्थ गौतम).
In Rama-centric traditions of Hinduism, he is considered the Supreme Being.
- Ramayana (रामायणम्, Rāmāyaṇam) is one of the two major Sanskrit epics of Ancient India (dated variously from 5th to 1rst Century BCE), the other being the Mahabharata (महाभारतम्, Mahābhārata).
The epic, traditionally ascribed to the Rishi Valmiki (ऋषि वाल्मीकि), narrates the life of Rama (राम), the legendary prince of the Kosala Kingdom (कोसला किंगडम).

In the Hindu Puranas (पुराण), Varuna (वरुण) is the God of Oceans, his vehicle is a Makara (मकर / part fish, part land creature) and his weapon is a Pasha (पाशा / noose, rope loop).
He is the Guardian Deity of the Western Direction.

In some texts, he is the father of the Vedic (वैदिक) sage, Vasishtha (वशिष्ठ).
- Puranas (पुराण / "ancient, old") is a vast genre of Indian Literature about a wide range of topics, particularly myths, legends and other traditional lore.
- Vashishtha (वशिष्ठ) is one of the oldest and most revered Vedic (वैदिक) Rishis (ऋषि / an accomplished and Enlightened Person).
He is one of the Saptarishis (सप्तर्षी / Seven great Rishis) of India.
Vashishtha is credited as the chief author of Mandala 7 (मंडल 7 / "book 7") of Rigveda (ऋग्वेद).
- Rishis (ऋषि / "Enlightened Persons") have composed hymns of the Shrutis (श्रुतिस / वेद, Vedas) and Smritis (स्मृतियों / उपनिषद, Upanishads - रामायणम्, Ramayan - महाभारतम्, Mahabharat).

Varuna (वरुण) is also mentioned in the Tamil (தமிழ் / a Dravidian language predominantly spoken by the Tamil people of India and Sri Lanka) grammar work Tolkāppiyam (தொல்காப்பியம்), as the God of Sea and Rain.

The Tolkāppiyam (தொல்காப்பியம் / "Paleo-literature" / the earliest extant work of Tamil Literature and linguistics / 3rd century BCE) divides the people of Ancient Tamilakam (தமிழகம் /Ancient Tamil Country) into 5 Sangam Landscape (அகத்திணை / "inner classification") divisions: Kurinji (குறிஞ்சி), Mullai (முல்லை), Paalai (பாமாலை), Marutham (கட்டிடத்திலுள்ள) and Neithal (நெய்தல்).
Each landscape are designated with different gods.
Neithal (நெய்தல்) is described as a seashore landscape occupied by fishermen and sea traders, with the God of Sea and Rain, Varunan (வரமுனான்) or Kadalōn (கடலான்).

"Varuna" means: "Water which donates the Ocean", in the Tamil language (தமிழ்).

The Pali Canon of the Theravada school recognizes Varuna (वरुण) as a King of the Devas (वेद) and companion of Sakka (सक्का), Pajāpati (प्रजापति) and Isāna (ईशान).

In the battle against the Asuras (असुर), the Devas (वेद) of Tāvatiṃsa (ट्रेएट्रिम्सा) were asked to look upon the banner of Varuna (वरुण) in order to have all their fears dispelled (S.i.219).
- The Pāli Canon is the standard collection of scriptures in the Theravada Buddhist tradition, as preserved in the Pāli language.
It is the most complete extant early Buddhist canon.
It derives mainly from the Tamrashatiya school.
-Theravāda ("School of the Elders") is the most commonly accepted name of Buddhism's oldest extant school.
- Tāvatiṃsa (ट्रेएट्रिम्सा / "belonging to the thirty-three") is an important world of the Devas (वेद) in Hindu and Buddhist Cosmology.

The Tevijja Sutta (तेविजा सुत) mentions Varuna (वरुण) among Indra (इन्द्र), Soma (सोम), Isāna (ईशान), Pajāpati (प्रजापति), Yama (यम) and Mahiddhi (महिदाधी) as Gods that are invoked by the Brahmins (ब्राह्मण).
- Brahmin (ब्राह्मण) is a varna (वर्ना / "class") in Hinduism, specializing as priests, teachers (आचार्य, acharya) and protectors of sacred learning across generations.
The traditional occupation of Brahmins (ब्राह्मण) was that of priesthood at the Hindu temples or at socio-religious ceremonies and rite of passage rituals such as solemnizing a wedding with hymns and prayers.
Theoretically, the Brahmins (ब्राह्मण) were the highest ranking of the four social classes.
In practice, Indian texts suggest that Brahmins (ब्राह्मण) were agriculturalists, warriors, traders and have held a variety of other occupations in the Indian subcontinent.

The Ātānātiya Sutta (ऐटानेया सुत) lists Varuna (वरुण) among the Yaksha (अक्षय) chiefs.
- Atanatiya Sutta (ऐटानेया सुत) is the 32nd Sutta (सुत) described in the Digha Nikaya (दीघा निकाया / "Long Discourses of Buddha").
It is a poem for protection from evil spirits presented to Buddha by King Vessavana (राजा वेसावना / one of the Four Heavenly Kings).
- Yaksha (अक्षय) are a broad class of nature-spirits, usually benevolent, but sometimes mischievous or capricious, connected with water, fertility, trees, the forest, treasure and wilderness.
They appear in Hindu, Jain and Buddhist texts, as well as Ancient and Medieval era temples of South Asia and Southeast Asia as Guardian Deities.
The feminine form of the word is Yakṣī (याकसी) or Yakshini (याख्यसी, Yakṣiṇī).

Buddhaghosa (बुद्धघोस / a 5th-century Indian Theravada Buddhist commentator, translator and philosopher) states (SA.i.262) that Varuna (वरुण) is equal in age and glory (वैना, vanna) with Sakka (सक्का) and takes the third seat in the assembly of Devas (वेद).

In East Asian Buddhism, Varuna (वरुण) is a Dharmapāla (धर्मपाल) and often classed as one of the twelve Devas (वेद / Japanese: 十二天, Jūniten).
He presides over the western direction.
- A Dharmapāla (धर्मपाल / "Dharma protector or defender") is a type of wrathful God in Buddhism.
The Dharmapālas (धर्मपाल) are also known as the Defenders of the Law (Dharma), or the Protectors of the Law.

Varuna (वरुण) is found in Japanese Buddhist Mythology as "Suiten" (水天 / "Water Deva").
He is included with the other eleven Devas (वेद / Japanese: 十二天, Jūniten), which include: Taishakuten (帝釈天 / शक्र, Śakra - इन्द्र, Indra), Fūten (フテン / वायु, Vāyu), Enmaten (エンマテン / यम, Yama), Rasetsuten (ラセツテン / निऋती, Nirṛti - राक्षस, Rākṣasa), Ishanaten (イシャナテン / ईशान, Īśāna), Bishamonten (毘沙門天 / वैसरावना, Vaiśravaṇa - कुबेर, Kubera), Katen (カテン / अग्नि, Agni), Bonten (ボンテン / ब्रह्मा, Brahmā), Jiten (事典 / पृथ्वी, Pṛthivī), Nitten (日展 / सूर्य, Sūrya - आदित्य, Āditya), and Gatten (ガッテン / चन्द्र, Chandra).

Varuna (वरुण) is also worshipped in Japan's Shinto (神道) Religion.
One of the Shinto (神道) shrines dedicated to him is the Suitengū (水天宮 / "Palace of Suiten") in Tokyo.

After the Japanese Emperor issued the Shinbutsu bunri (神仏分離), the separation of Shinto (神道) and Buddhist practices as part of the Meiji Restoration (明治維新) Varuna (वरुण) / Suiten (水天) was identified with the Japanese Supreme God, Amenominakanushi (天御中主 or 天之御中主神, "Heavenly Ancestral God of the Originating Heart of the Universe").

Varuna (वरुण) is also found in Jainism (जैन धर्म, Jain Dharma / an Ancient Indian Religion).