The Duchy of Silesia (Polish: Księstwo śląskie, German: Herzogtum Schlesien, Czech: Slezské knížectví) with its capital at Wrocław was a medieval duchy located in the historic Silesian region of Poland. Soon after it was formed under the Piast dynasty in 1138, it fragmented into various Silesian duchies. In 1327, the remaining Duchy of Wrocław as well as most other duchies ruled by the Silesian Piasts passed to the Kingdom of Bohemia as Duchies of Silesia. The acquisition was completed when King Casimir III the Great of Poland renounced his rights to Silesia in the 1335 Treaty of Trentschin.