Konrad I Mazowiecki

Konrad I
19th century drawing by Jan Matejko
High Duke of Poland
Reign	1229–1232
Predecessor	Władysław III Spindleshanks
Successor	Henry I the Bearded
Reign	1241–1243
Predecessor	Bolesław II Rogatka
Successor	Bolesław V the Chaste
Duke of Masovia
Reign	1194–1247
Predecessor	Casimir II the Just Helen of Znojmo (regent)
Successor	Boleslaus I
Born	c. 1187/88
Died	31 August 1247
Spouse	Agafia of Rus
Issue	Boleslaus I of Masovia Casimir I of Kuyavia Siemowit I of Masovia
House	House of Piast
Father	Casimir II the Just
Mother	Helen of Znojmo

Konrad I of Masovia (Polish: Konrad I Mazowiecki) (ca. 1187/88 – 31 August 1247), from the Polish Piast dynasty, was the sixth Duke of Masovia and Kujawy from 1194 until his death as well as High Duke of Poland from 1229 to 1232 and again from 1241 to 1243.

He was the youngest son of High Duke Casimir II the Just of Poland and Helen of Znojmo, daughter of the Přemyslid duke Konrad II of Znojmo (ruler of the Znojmo Appanage in southern Moravia, part of Duchy of Bohemia). His maternal grandmother was Maria of Serbia, apparently a daughter of the pre-Nemanjić župan Uroš I of Rascia.

After his father's death in 1194, Konrad was brought up by his mother, who acted as regent of Masovia. In 1199 he received Masovia and in 1205 also the adjacent lands of Kuyavia. In 1205, he and his brother, Duke Leszek I the White of Sandomierz, had their greatest military victory at Battle of Zawichost against Prince Roman the Great of Galicia–Volhynia. The Ruthenian army was crushed and Roman was killed in battle. The Rurik princess Agafia of Rus became his wife.