Jyotisha or Jyotishya (ज्योतिष, ज्योतिश्या / "light, heavenly body") is the traditional Hindu system of Astrology, also known as Hindu Astrology (हिंदू ज्योतिष) or Vedic Astrology (वैदिक ज्योतिष).

Vedanga Jyotishya (वेडांगा ज्योतिश्या) is one of the earliest texts about Astronomy within the Vedas (वेद / "knowledge").

- The Vedas (वेद) 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 (वेद) to be apauruṣeya (अपौरुषेय), which means "not of a man, superhuman" and "impersonal, authorless".

However, it is believed that the Horoscopic Astrology practiced in the Indian subcontinent came from Hellenistic influences, post-dating the Vedic period (c. 1500 - c. 500 BCE).

In the mythologies Ramayana (रामायणम्, Rāmāyaṇa) and Mahabharata (महाभारतम्, Mahābhārata) are multiple references about Electional Astrology (Event Astrology), omens, dreams and physiognomy.

- Electional Astrology (Event Astrology) is a branch found in most traditions of Astrology according to which, a practitioner decides the most appropriate time for an event, based on the astrological auspiciousness of that time.

- Ramayana (रामायणम्, Rāmāyaṇam) is one of the two major Sanskrit (संस्कृत) 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, Rāma / रामचंद्र, Ramachandra / Major Deity of Hinduism / Seventh avatar of the god Vishnu, विष्णु), the legendary prince of the Kosala Kingdom (कोसला किंगडम).

- Rishis (ऋषि / "Enlightened Persons") have composed hymns of the Shrutis (श्रुतिस / वेद, Vedas) and Smritis (स्मृतियों / उपनिषद, Upanishads - रामायणम्, Ramayan - महाभारतम्, Mahabharat).

- Mahabharata (महाभारतम्, Mahābhārata) is a major Sanskrit (संस्कृत) epic of Ancient India (originated: 8th and 9th Centuries BCE / dated: early Gupta period, c. 4th century CE).
Mahabharata (महाभारतम्, Mahābhārata) narrates the struggle between two groups of cousins in the Kurukshetra War (कुरुक्षेत्र युद्ध / 5561 - c. 950 BCE) and the fates of the Kaurava (कौरव) and the Pāṇḍava (पाण्डव) Princes, and their succession.
Traditionally, the authorship of the Mahabharata (महाभारतम्, Mahābhārata) is attributed to Vyāsa (व्यास / "Compiler") or Veda Vyāsa (वेदव्यास, veda-vyāsa / "the one who classified the Vedas") or Krishna Dvaipāyana (कृष्ण पीयाना / referring to his dark complexion and birthplace).
Vyāsa (व्यास) is considered to be one of the seven Chiranjivins (चिरञ्जीवि / long-lived or immortals), who are still in existence according to Hindu tradition.

- The Ramayana (रामायणम्, Rāmāyaṇam) and the Mahabharata (महाभारतम्, Mahābhārata) form Hindu Itihasa (हिंदू इटीहासा / "Hindu History").

Jyotiṣa (ज्योतिष, Jyotisha / ज्योतिश्या, Jyotishya) is one of the Vedāṅga (वेदाङ्ग / "Limbs of the Veda"), the six auxiliary disciplines used to support Vedic (वैदिक) rituals.

Early Jyotiṣa (ज्योतिष, Jyotisha / ज्योतिश्या, Jyotishya) is concerned with the preparation of a calendar to determine dates for sacrificial rituals, with nothing written regarding planets.

There are mentions of eclipse-causing "demons" in the Atharvaveda (अथर्ववेद) and Chāndogya Upaniṣad (छांदोग्योपनिषद्, Chāndogyopaniṣad), the latter mentioning Rāhu (राहु / a shadow entity believed responsible for eclipses and meteors).

The term "graha" (ग्राहा), which is now taken to mean "planet", originally meant "demon".

The foundation of Hindu Astrology is the notion of bandhu (बैंडु / "tie") of the Vedas (वेद), which is the connection between the microcosm and the macrocosm (the outer and the inner world).
Practice relies primarily on the Sidereal Zodiac (नारायण राशि / Nirayana Rashi), which differs from the Tropical Zodiac (सयाना राशि / Sāyana Rashi) used in Western (Hellenistic) Astrology in that an ayanāṁśa (अयानामसा) adjustment is made for the gradual precession of the Vernal Equinox.

- Ο ayanāṁśa (अयानामसा) is a Sanskrit (संस्कृत) term in Indian Astronomy for the amount of precession / the longitudinal difference between the Tropical, and Sidereal zodiacs.

- Tropical Astrology is based on the orientation of the Earth relative to the Sun and Planets of the Solar System, while Sidereal Astrology deals with the position of the Earth relative to both of these, as well as the Stars of the Celestial Sphere.

Hindu Astrology includes several nuanced sub-systems of interpretation and prediction with elements not found in Hellenistic Astrology, such as its system of Lunar Mansions (नक जात्रा, Nakṣatra / a segment of the ecliptic through which the Moon passes in its orbit around the Earth).

- A Nakshatra (नक जात्रा) is one of 28 (sometimes also 27) sectors along the ecliptic.
Their names are related to a prominent Star or Asterisms in or near the respective sectors.

It was only after the transmission of Hellenistic Astrology that the order of Planets in India was fixed in that of the seven-day week.

Hellenistic Astrology and Astronomy also transmitted the twelve Zodiacal Signs beginning with Aries and the twelve Astrological Places beginning with the Ascendant.

The first evidence of the introduction of Greek Astrology to India is the Yavanajātaka (यवनाजतका / स्फूजीधवजा, Sphujidhvaja / an ancient text in Indian Astrology / "Sayings of the Greeks") which dates to the early centuries CE.
The Yavanajātaka (यवनाजतका) was translated from Greek to Sanskrit (संस्कृत) by Yavaneśvara (यावनेवरा) during the 2nd century CE, and is considered the first Indian Astrological treatise in the Sanskrit language (संस्कृत).
However the only version that survives is the verse version of Sphujidhvaja (स्फूजीधवजा) which dates to 270 AD.

The first Indian Astronomical text to define the weekday was the Āryabhaṭīya of Āryabhaṭa (आर्यभट्टिया के आर्यभट्ट / a Sanskrit Astronomical treatise, the magnum opus and only known surviving work of the 5th Century Indian mathematician, Aryabhata / 476 AD).

According to historians, Indian astronomers must have been occupied with the task of Indianizing and Sanskritizing Greek Astronomy during the 300 or so years between the first Yavanajataka (यवनाजतका) and the Āryabhaṭīya (आर्यभट्टिया).
The Astronomical texts of these 300 years are lost.

The later Pañcasiddhāntikā of Varāhamihira (पैनकासिधांटिका के वराहमिहिरा / a Sanskrit Astronomical work of the Hindu polymath, Varāhamihira) summarizes the five known Indian Astronomical schools of the 6th Century.

Indian Astronomy preserved some of the older pre-Ptolemaic elements of Greek Astronomy.
The main texts upon which classical Indian Astrology is based, are early Medieval compilations, notably the Bṛhat Parāśara Horāśāstra (ब्रहत पाराशर होरास्त्र) and Sārāvalī (सरावली) by Kalyāṇavarma (कल्याणवर्मा).

- The Horāshastra (होरास्त्र) is a composite work of 71 chapters, of which the first part (chapters 1-51) dates to the 7th to early 8th Centuries and the second part (chapters 52-71) to the later 8th Century.

- The Sārāvalī (सरावली) likewise dates to around 800 CE.