Leszek of Masovia (, also Lestek) (b. ca. 1162 - d. 1186) was a Polish prince from the Piast dynasty, the Duke of Masovia from 1173 until his death. He was the only son of Bolesław IV the Curly, Duke of Masovia and High Prince of Poland, to survive his father. After his father's death he inherited Masovia. At the beginning, Leszek ruled under the guardianship of his uncle Casimir II the Just. He was a man of poor health. For a short time he supported his other uncle, Mieszko III the Old, but later decided to reconcile with Casimir II, who after Leszek's death inherited his duchy. Early life Older Polish historians, like Oswald Balzer, named him Leszko, which is now considered as incorrect. The correct form is ending with "ek". In a document written in Latin, Leszek was mentioned as Lizstek (1177). Most Polish historians use the version "Leszek", but some modern Polish historians started to use the version Lestek. Historian Józef Mitkowski stated that Leszek was named thanks to the courtly tradition preserved by Gallus Anonymus in his Cronicae Polonorum, but as pointed out by historian and genealogist Kazimierz Jasiński, he could be named after the eldest full-brother of his father, who died in his youth before 1131. In the past historians were unsure which wife of Bolesław IV the Curly was the mother of Leszek: the first, Wierzchosława, daughter of St. Vsevolod, Prince of Novgorod and Pskov, or the second, Maria. According to chronicler Jan Długosz, Leszek was the son of Anastazja, a princess of Halych and the first wife of Bolesław IV. Oswald Balzer found this information to be incorrect, as the first wife of Bolesław IV was named Wierzchosława and she was not from Halych. According to the historian Miron Korduba, Leszek was the son of Maria. Józef Mitkowski and Kazimierz Jasiński supposed that he was the son of the first wife of Bolesław IV rather than the second. However, after the discovery of coins on which Leszek noted his parents as BOL (Bolesław IV the Curly) and ANA (Anastazja), it became clear that he was the son of his father's first marriage, as Wierzchosława is mentioned in some sources as Anastazja. The date of Leszek's birth is unknown. According to Jan Długosz, writing in the 15th century, he was born in 1158. Historian Oswald Balzer stated that Leszek was born between 1160 and