Ryōkan was born in the village of Izumozaki in Echigo Province (now Niigata Prefecture) in Japan to the village headman. He renounced the world at an early age to train at nearby Sōtō Zen temple Kōshōji, refusing to meet with or accept charity from his family. Once the Zen master Kokusen visited the temple, and Ryōkan was deeply impressed with his demeanor. He solicited permission to become Kokusen's disciple. Kokusen accepted, and the two returned to Entsūji monastery in Tamashima (now Okayama Prefecture).

It was at Entsūji that Ryōkan attained satori and was presented with an Inka by Kosusen. Kokusen died the following year, and Ryōkan left Entsūji to embark on a long pilgrimage. He lived much of the rest of his life as a hermit, and did not return to monastic life.

He was originally ordained as Ryōkan Taigu. Ryō means "good", kan means "broad", and Taigu means "great fool"; Ryōkan would thus translate as "broad-hearted generous fool", referring to qualities that Ryōkan's work and life embodies.

Ryōkan spent much of his time writing poetry, calligraphy, and communing with nature. His poetry is often very simple and inspired by nature. He loved children, and sometimes forgot to beg for food because he was playing with the children of the nearby village. Ryōkan refused to accept any position as a priest or even as a "poet", which shows his great humility. In the tradition of Zen his quotes and poems show he had a good sense of humour and didn't take himself too seriously. However his poetry also gives illumining insights into the practise of Zen.