Konrad I of Mazovia (1187–31.08.1247) – Polish Duke of the time of feudal fragmentation, representative of the Piast dynasty. Duke of Kuyavia (1202–1247), Sieradz, Krakow (1229–1232, 1241–1243). Founder of the Mazovia Duchy in the structure of Poland (1207–1247), the youngest son of Krakow Duke Kazimierz II the Just and Olena Vsevolodivna, daughter of Prince Vsevolod Mstyslavych of Belz (according to other version, of Rostyslav Mstyslavych, Prince of Smolensk and Kyiv).
Younger brother of Leszek the White. Was married to Ahafia, daughter of Prince Sviatoslav Ihorovych of Volyn. Closely collaborated with the Teutonic Order of Crusaders, in 1226 transferred the Khelm land of Poland to the Teutonic Order. In the mid-1230 s he conflicted with Prince Danylo of Halych-Volyn and took side of his enemy Prince Mykhailo Vsevolodovych of Chernihiv. In 1237–1238 Konrad and Crusaders were defeated by Prince Danylo Romanovych in the battle at Drohychyn and had to return the Drohychyn land over the Buh (Podlasie voivodeship, the territory of contemporary Poland), occupied by Poland at the end of the 12 th c. Taking advantage of the death of Henryk II the Pious (during the invasion of Batu Khan), he occupied Krakow on July 10, 1241, and became the Duke of Krakow (1241–1243). However, after the battle at Sukhodil on May 23, 1243, where he was defeated by Duke Bolesław V the Meek, had to leave Krakow and return to Mazovia.