Maha-vakya is “a great sentence” from the Hindu scriptures the Upanishads that is short but expresses “a final truth.” It does that by affirming identity between the individual self on the one hand and Brahman the ground of Being, the universal spirit, on the other, in statements such as “I am Brahman.” This dissertation investigates the origins and early history of maha-vakya in the Advaita Vedanta school of interpretation, from the 5th to the 11th century AD. ,The idea itself is one of the most common notions in Hinduism. Scholars refer to it often, but there has been no dedicated study of its origin, and only few tangential attempts at understanding its meaning. The general tendency has been either to assume that maha-vakyas were just “always there,” or to associate them with the great 8th century philosopher Śaṅkara. ,Following the growing scholarly trend of studying the two schools of Hindu exegesis, Mimamsa and Vedanta, as belonging to the same intellectual universe and sharing the general approach to and categories of interpretation, I show in the dissertation that: (1) an explicit theory of Upanishadic maha-vakyas was for the first time proposed not by Śaṅkara, but by the 11th century Vedantin Sarvajñātman; (2) an explicit but not theorized notion of maha-vakya can be traced to the other school of Hindu exegesis, Mimamsa, the 5th century hermeneut Śabara and his followers Kumārila and Prabhākara, where maha-vakya did not refer to the short Upanishadic identity statements, but to larger textual units of the injunctive kind; (3) Sarvajñātman modeled the notion of Upanishadic maha-vakyas on the Mimamsa blueprint, fitting Vedanta building blocks into a Mimamsa structure; (4) the Upanishadic identity statements were only formally short: they were cryptic ellipses whose elaboration requires the full Upanishadic corpus; (5) the key element in maha-vakya, both in the Mimamsa blueprint and the Vedanta adaptation, was finality of meaning. ,The dissertation is an essay in the history of ideas, and it unravels the intellectual developments that had to happen for Sarvajñātman to outline a theory of maha-vakya. Its first part explores the notion of “scripture” in the two schools and introduces the important categories of interpretation. In the second part, I examine the prominent pre-Śaṅkara readings of the Upanishads and show that early Vedantins interpreted the Upanishads as texts that promote liberation from transmigration through meditative absorption based on injunctive statements. I show in the third part that Śaṅkara reinterpreted the Upanishads in the light of the identity statements and replaced meditation with philosophical inquiry with a teacher. Finally, in part four I demonstrate that Sarvajñātman reworked the old Mimamsa notion of maha-vakya to make it fit the identity statements of the Upanishads. ,Maha-vakyas came into sharp prominence during the ninetieth and twentieth century attempts at fashioning Hinduism as a single, coherent religion, and they were explicitly used by the likes of Mahatma Gandhi and Bhaktivedanta Swami. Today, maha-vakyas are staple items in various Hindu religious movements, both in India and in the West. They are used as interpretation devices, meditation props, or just mantras for spiritual exercise, and many get them in their daily social media feed. The dissertation is the first study of the early history of the notion in classical Hindu thought, and a groundwork for better appreciation of the modern Hindu hermeneutic situation.