Theodosius of Kyiv was an 11th-century monk who played a fundamental role in the development of monasticism in Kievan Rus'. Alongside Anthony of Kyiv, he established the Kyiv Caves Lavra, a significant religious site. He is primarily recognized for introducing the Studite rule to the region, which provided a structured way of life for monks. Born in Vasylkiv, he served as abbot of the monastery, where he emphasized ascetic practices such as fasting and prayer.