Matsyendranātha, also known as Matsyendra or Macchindranāth, was a revered saint and yogi in Buddhist and Hindu traditions. He is credited with reviving hatha yoga and is considered the founder of the natha sampradaya. Matsyendranātha received teachings from Shiva and is associated with Kaula Shaivism. He is regarded as one of the eighty-four mahasiddhas and is considered the guru of Gorakshanath, another important figure in hatha yoga. Matsyendranātha is revered by Hindus and Buddhists and is sometimes seen as an incarnation of Avalokiteśvara.

The details of Matsyendranātha's early life are unclear, with legends differing on his birthplace. Some sources suggest he was a fisherman from Kamarupa or North Bengal. According to legends, Matsyendranātha was born under an inauspicious star and was thrown into the ocean by his parents. He was swallowed by a fish, where he lived for many years and learned the secrets of yoga from Shiva. After twelve years, he emerged from the fish as an enlightened Siddha. Other versions of the legend describe Matsyendranātha being born as a fish and later transformed into a Siddha by Shiva.

Matsyendranātha is attributed with composing Hatha and Tantric works, including the Kaulajñānanirnāya, Matsyendrasamhita, and Akula-Viratantra, which are among the earliest texts on hatha yoga in Sanskrit. It is theorized that many works were attributed to him posthumously. Matsyendranātha is said to have had eight disciples, including Gorakshanath, Jalandharnath, and Kanifnath.

In Nepal, Matsyendranātha is worshiped as Macchindranāth, the god of rain, by both Hindus and Buddhists. His temple, known as Rato Machhindranath Temple, is located in Patan and is the center of the annual Bunga Dyah Jatra or Rato Macchindranath Jatra, a month-long chariot procession celebrated to show respect to the rain god. The chariot carrying the image of Macchindranath is pulled through the streets of Patan, and the festival concludes with the Bhoto Jatra, where a sacred vest is shown to the crowds. After the festival, the chariot is dismantled, and the deity is taken to the village of Bungamati, regarded as his birthplace, where he stays for the next six months.

Temples dedicated to Matsyendranātha can also be found in various parts of India, including Maharashtra, Madhya Pradesh, and Karnataka.

Matsyendranātha's legend has been depicted in Indian cinema, with films such as "Maya Machhindra" made in multiple languages during different periods. Additionally, the Dasam Granth, a religious text, includes a discourse between Matsyendranātha and Paras Nath.