Medzhybizh is first mentioned in chronicles as an estate in Kievan Rus. It was given to Prince Svyatoslav by the prince of Kiev in the year 1146. In 1148, ownership transferred to Rostyslav, the son of Yuri Dolgoruky. The wooden fortress that stood there was destroyed in 1255. After the Mongol incursion, by 1360, the town and surrounding territory passed into the hands of the Lithuanians. The town suffered from numerous attacks by the Tatars in 1453, 1506, 1516, 1546, 1558, 1566, and 1615. In 1444 the town was incorporated into lands administered by Poland. In the 1500s, the territory was controlled by the Sieniawski and Potocki Polish noble families. In 1511 work began to replace the wooden palisades with massive stone fortifications, many of which can still be seen today. A dam was built