The Mahābhārata (/məˌhɑːˈbɑːrətə, ˌmɑːhə-/ mə-HAH-BAR-ə-tə, MAH-hə-; Sanskrit: महाभारतम्, IAST: Mahābhāratam, pronounced [mɐɦaːˈbʱaːrɐt̪ɐm]) is a smriti text (also described as a Sanskrit epic) from ancient India, one of the two important epics of Hinduism known as the Itihasas, the other being the Ramayana. It narrates the events and aftermath of the Kurukshetra War, a war of succession between two groups of princely cousins, the Kauravas and the Pāṇḍavas. It contains philosophical and devotional material, such as a discussion of the four "goals of life" or puruṣārtha (12.161). Among the principal works and stories in the Mahābhārata are the Bhagavad Gita, the story of Damayanti, the story of Shakuntala, the story of Pururava and Urvashi, the story of Savitri and Satyavan, the story of Kacha and Devayani, the story of Rishyasringa and an abbreviated version of the Rāmāyaṇa, often considered as works in their own right.

Traditionally, the authorship of the Mahābhārata is attributed to Vyāsa. There have been many attempts to unravel its historical growth and compositional layers. The bulk of the Mahābhārata was probably compiled between the 3rd century BCE and the 3rd century CE, with the oldest preserved parts not much older than around 400 BCE. The text probably reached its final form by the early Gupta period (c. 4th century CE).

The title is translated as "Great Bharat (India)", or "the story of the great descendants of Bharata", or as "The Great Indian Tale". The Mahābhārata is the longest epic poem known and has been described as "the longest poem ever written". Its longest version consists of over 100,000 shlokas (verses) or over 200,000 individual lines (each shloka is a couplet), and long prose passages. At about 1.8 million words in total, the Mahābhārata is roughly ten times the length of the Iliad and the Odyssey combined, or about four times the length of the Rāmāyaṇa. Within the Indian tradition it is sometimes called the fifth Veda.

The epic is traditionally ascribed to the sage Vyasa, who is also a major figure in the epic. Vyasa described it as being an itihasa (transl. history). He also describes the Guru–shishya tradition, which traces all great teachers and their students of the Vedic times.

The first section of the Mahābhārata states that it was Ganesha who wrote down the text to Vyasa's dictation, but this is regarded by scholars as a later interpolation to the epic and the "Critical Edition" does not include Ganesha.

The epic employs the story within a story structure, otherwise known as frametales, popular in many Indian religious and non-religious works. It is first recited at Takshashila by the sage Vaisampayana, a disciple of Vyasa, to the King Janamejaya who was the great-grandson of the Pandava prince Arjuna. The story is then recited again by a professional storyteller named Ugrashrava Sauti, many years later, to an assemblage of sages performing the 12-year sacrifice for the king Saunaka Kulapati in the Naimisha Forest.

The text was described by some early 20th-century Indologists as unstructured and chaotic. Hermann Oldenberg supposed that the original poem must once have carried an immense "tragic force" but dismissed the full text as a "horrible chaos." Moritz Winternitz (Geschichte der indischen Literatur 1909) considered that "only unpoetical theologists and clumsy scribes" could have lumped the parts of disparate origin into an unordered whole.

Research on the Mahābhārata has put an enormous effort into recognizing and dating layers within the text. Some elements of the present Mahabharata can be traced back to Vedic times. The background to the Mahābhārata suggests the origin of the epic occurs "after the very early Vedic period" and before "the first Indian 'empire' was to rise in the third century B.C." That this is "a date not too far removed from the 8th or 9th century B.C." is likely. The Mahabharata started as an orally-transmitted tale of the charioteer bards. It is generally agreed that "Unlike the Vedas, which have to be preserved letter-perfect, the epic was a popular work whose reciters would inevitably conform to changes in language and style," so the earliest 'surviving' components of this dynamic text are believed to be no older than the earliest 'external' references we have to the epic, which include a reference in Panini's 4th century BCE grammar Ashtadhyayi 4:2:56. Vishnu Sukthankar, editor of the first great critical edition of the Mahābhārata, commented: "It is useless to think of reconstructing a fluid text in an original shape, based on an archetype and a stemma codicum. What then is possible? Our objective can only be to reconstruct the oldest form of the text which it is possible to reach based on the manuscript material available." That manuscript evidence is somewhat late, given its material composition and the climate of India, but it is very extensive.