Matsyendranātha, also known as Matsyendra, Macchindranāth, Mīnanātha and Minapa (early 10th century) was a saint and yogi in a number of Buddhist and Hindu traditions. He is considered the revivalist of hatha yoga as well as the author of some of its earliest texts. He is also seen as the founder of the natha sampradaya, having received the teachings from Shiva. He is associated with Kaula Shaivism. He is also one of the eighty-four mahasiddhas and considered the guru of Gorakshanath, another known figure in early hatha yoga. He is revered by both Hindus and Buddhists and is sometimes regarded as an incarnation of Avalokiteśvara.

In the Siddhar tradition of Tamil Nadu, Matsyendranatha is revered as one of the 18 Siddhars of yore, and is also known as Machamuni. The Kasi Viswanathar Temple in Thiruparankundram, Madurai, Tamil Nadu is home to his Jiva Samadhi. In Nepal, Matsyendranatha is a highly revered deity, and the largest chariot festival in the world is dedicated to him in the valley of Kathmandu as a Buddhist-Hindu syncretic tradition.

Little is known about the life of Matsyendranatha: he is also called Minanatha and he is also associated with Lui-pa, all of whose names translate as 'Lord of the Fishes'. Legends vary in describing his birthplace. Giuseppe Tucci states, on the authority of two Tibetan works - the Siddha (Wylie: grub thob) and Taranatha's "Possessing the Seven Transmissions" (Wylie: bka' babs bdun ldan) - that Matsyendranātha, who is seen in Tibet as an avatar of Avalokiteśvara, was a from Kaibarta or fishermen community of Kamarupa. Other sources give his birthplace as Barisal ( then Chandradwip). According to inscriptions found in Nepal in the ancient Newari colony of Bungmati, the home of Machhindranath Chariot Jatra, his shrine was brought from Assam in India. He is mentioned in the Sabaratantra as one of the twenty-four Kapalika Siddhas.

Legends have it that Matsyendranatha was born under an inauspicious star. This warranted his parents to throw the baby into the ocean. It was there that the baby was swallowed by a fish where he lived for many years. The fish swam to the bottom of the ocean where Shiva was imparting the secrets of yoga to his consort, Parvati. Upon overhearing the secrets of yoga, Matsyendranatha began to practice yoga sadhana inside the fish's belly. After twelve years he emerged as an enlightened Siddha. This is given as the origin of his name 'Lord of the Fishes' or 'He Whose Lord is the Lord of the Fishes'. Other versions of the legend exist, including one in which Matsyendranatha was born as a fish and turned into a Siddha by Shiva. Tibetan renditions of the story tell of a fisherman-turned-Siddha named Mina, who is eaten by a fish while working in the Bay of Bengal. Some scholars draw parallels between this legend and the Biblical story of Jonah and the Whale.

Another legend says that, when Gorakshanath visited Patan, in Nepal, he captured all the rain-showering serpents of Patan and started to meditate after he was disappointed by the locals as they did not grant him any alms on his request. As a result, Patan faced drought for a long time. The king of Patan, on the advice of his advisers, invited Matsyendranatha, Gorakshanath's guru, to Patan. When Gorakshanath learned that his teacher was in Patan, he released the rain showering serpents and went to see him. As soon as the rain-showering serpents were set free, Patan again got plenty of rainfall every year. After that day, the locals of Patan worshiped Matsyendranatha as the god of rain.

Matsyendranatha is credited with composing Hatha and Tantric works such as the Kaulajñānanirnāya ("Discussion of the Knowledge Pertaining to the Kaula Tradition"), the Matsyendrasamhita and "Akula-Viratantra", some of the earliest texts on hatha yoga in Sanskrit in the eleventh century. James Mallinson, Alexis Sanderson, David Gordon White and others theorize that many works were attributed to him posthumously.

Matsyendranatha is listed as having eight disciples. The list of his disciples varies between different temples and lineages, but includes Gorakshanath, Jalandharnath, Kanifnath (Kanhoba), Gahininath, Bhartri Nath, Revan Nath, Charpatinath and Naganath. Along with Matsyendranatha, they are called the Navnath. While Gorkshanath is considered a direct disciple of Matsyendranatha, it is likely they lived hundreds of years apart.

Macchindranāth (or Bunga Dyah in Newari) is a god of rain worshiped by both Hindus and Buddhists in Nepal. Hindus regard him as an incarnation of Shiva while Buddhists regard him as an incarnation of Avalokiteśvara.The first original temple of Machhindranath is in a place called Bungamati while the second temple Macchindranāth lies in the southern part of the Patan Durbar Square since 1673.