Jonah of Yashezersk was a Russian monastic founder of the late sixteenth century who established a monastery near Yash Lake (Yashezero) in the northern Russian wilderness. According to the synaxarion, he was born in the village of Shoksha, sixteen versts from the site of the monastery he later founded. He is numbered among the disciples of Saint Alexander of Svir, a major figure of northern Russian monasticism whose followers founded a network of monasteries among the lakes of the Olonets region.
The foundation of his monastery is dated to 1580, when a wooden church was built in honor of the Annunciation of the Theotokos and eight monks gathered around him to live the ascetic life. Jonah labored continually over the material upkeep of the community: to ease the catching of fish he dug a channel connecting Yash Lake with the nearby Lake Senno, and he rode the solitary forest paths in search of provisions for the brethren. By tradition he himself fashioned wooden vessels for liturgical use and gathered donations and ecclesiastical texts for the monastery.
The monastery was poor, and Jonah petitioned for relief from taxes, which was granted on 1 June 1589. The sources record that he was held in high regard by prominent churchmen of the region, including Metropolitan Isidore of Novgorod and Igumen James of the Solovki monastery. The synaxarion places his death in the late sixteenth or early seventeenth century; one tradition relates that he died in a cave a short distance from the monastery. He was buried at the Annunciation monastery he had founded, where his tomb came to be venerated as a place of healing. He is commemorated on September 22.