Konrad I of Masovia (Polish: Konrad I Mazowiecki; 1187? 1247), son of Casimir II and Helen of Moravia, was the 6th Duke of Masovia. After his father's death in 1194, Konrad was brought up by his mother. In 1199 he received Masovia and in 1202, Kuyavia. In 1205, he and his brother, Leszek I the White, had their greatest military victory at Battle of Zawichost against Roman the Great. The Ruthenian army was crushed and Roman was killed in battle. The Russian princess Agafia of Rus became his wife. His maternal grandmother (the princess-consort of Moravia, Znaim (part of Holy Roman Empire) was one Maria of Serbia, apparently a daughter of the pre-Nemanjic Zhupan dynasty.