John the Hairy was a sixteenth-century holy fool, also known as John the Merciful, who lived in Rostov Veliky. He was recognized for his ascetic lifestyle, characterized by constant prayer and profound humility. During his life, he faced numerous hardships and lacked a permanent home, often finding temporary shelter with elderly widows or at the residence of his spiritual mentor. He is remembered for his spiritual influence on others, including the hermit Irenarchus, through his patient and dedicated devotion.