Madhvacharya (IAST: Madhvācārya; pronounced [mɐdʱʋaːˈtɕaːrjɐ]; 1199–1278 CE or 1238–1317 CE), also known as Purna Prajna (IAST: Pūrṇa-Prajña) and Ānanda Tīrtha, was an Indian philosopher, theologian and the chief proponent of the Dvaita (dualism) school of Vedanta. Madhva called his philosophy Tattvavāda meaning "arguments from a realist viewpoint".

Madhvacharya was born at Pajaka near Udupi on the west coast of Karnataka state in 13th-century India. As a teenager, he became a Sanyasi (monk) joining Brahma-sampradaya guru Achyutapreksha, of the Ekadandi order. Madhva studied the classics of Hindu philosophy, and wrote commentaries on the Principal Upanishads, the Bhagavad Gita and the Brahma Sutras (Prasthanatrayi), and is credited with thirty seven works in Sanskrit. His writing style was of extreme brevity and condensed expression. His greatest work is considered to be the Anuvyakhyana, a philosophical supplement to his bhasya on the Brahma Sutras composed with a poetic structure. In some of his works, he proclaimed himself to be an avatar of Vayu, the son of god Vishnu.

Madhvacharya was a critic of Adi Shankara's Advaita Vedanta and Ramanuja's Vishishtadvaita Vedanta teachings. He toured India several times, visiting places such as Badrinath, Bengal, Varanasi, Dwaraka, Goa and Kanyakumari, engaging in philosophical debates and visiting Hindu centres of learning. Madhva established the Krishna Mutt at Udupi with a murti secured from Dwarka Gujarat in 1285 CE.

Madhvacharya's teachings are built on the premise that there is a fundamental difference between Atman (individual soul, self) and the Brahman (ultimate reality, God Vishnu), these are two different unchanging realities, with individual soul dependent on Brahman, never identical. His school's theistic dualism teachings disagreed with the monist teachings of the other two most influential schools of Vedanta based on Advaita's nondualism and Vishishtadvaita's qualified nondualism. Liberation, asserted Madhva, is achievable only through the grace of God. The Dvaita school founded by Madhva influenced Vaishnavism, the Bhakti movement in medieval India, and has been one of the three influential Vedānta philosophies, along with Advaita Vedanta and Vishishtadvaita Vedanta. Madhva's historical influence in Hinduism, state Kulandran and Kraemer: "has been salutary, but not extensive.“

The biography of Madhvacharya is unclear about his year of birth. Many sources date him to 1238–1317 period, but some place him about the 1199–1278 period.

Madhvācārya was born in Pajaka near Udupi, a coastal district in the present-day Indian state of Karnataka. Traditionally it is believed that his father's name is Naduillaya (Sanskrit: Madhyageha, Madhyamandira) and the name of his mother is unclear, although many sources variously claim it as Satyavati and Vedavati. Born in a Tulu Brahmin household, he was named Vāsudeva. Later he became famous by the names Purnaprajna, Anandatirtha and Madhvacharya (or just Madhva). Pūrnaprajña was the name given to him at the time of his initiation into sannyasa (renunciation), as a teenager. The name conferred on him when he became the head of his monastery was "Ānanda Tīrtha". All three of his later names are found in his works. Madhvācārya or Madhva are names most commonly found in modern literature on him, or Dvaita Vedanta related literature.

Madhva began his school after his Upanayana at age seven, and became a monk or Sannyasi in his teens, although his father was initially opposed to this. He joined an Advaita Vedanta monastery in Udupi (Karnataka), accepted his guru to be Achyutrapreksha, who is also referred to as Achyutraprajna in some sources. Madhva studied the Upanishads and the Advaita literature, but was unconvinced by its nondualism philosophy of oneness of human soul and god, had frequent disagreements with his guru, left the monastery, and began his own tattvavada movement based on dualism premises of Dvi – asserting that human soul and god (as Vishnu) are two different things. Madhva never acknowledged Achyutrapreksha as his guru or his monastic lineage in his writings. Madhva is said to have been clever in philosophy, and also to have been tall and strongly built.

Reality is twofold: independent and dependent things. The Lord Vishnu is the only independent thing.