Konrad I of Masovia (ca. 1187/88 â 31 August 1247), from the Polish Piast dynasty, was the sixth Duke of Masovia and Kuyavia from 1194 until his death as well as High Duke of Poland from 1229 to 1232 and from 1241 to 1243.
Konrad was the youngest son of High Duke Casimir II the Just of Poland and Helen of Znojmo, daughter of the Pà Âemyslid duke Conrad 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-NemanjiÃ à ¾upan Uroà ¡ 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 the adjacent lands of Kuyavia as well. 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 GaliciaâÂÂVolhynia. The Ruthenian army was crushed and Roman was killed in battle. The Rurik princess Agafia of Rus became his wife.
In an effort to enlarge his dominions, Konrad unsuccessfully attempted to conquer the adjacent pagan lands of Cheà Âmno in Prussia during a 1209 crusade with the consent of Pope Innocent III. In 1215, the monk Christian of Oliva was appointed a missionary bishop among the Old Prussians, his residence at Cheà Âmno however was devastated by Prussian forces the next year. Several further campaigns in 1219, 1222 failed, instead Konrad picked a long-term border quarrel with the Prussian tribes.
The duke's ongoing attempts on Prussia were answered by incursions across the borders of his Masovian lands, while Prussians were in the process of gaining back control over the disputed Cheà Âmno Land and even threatened Konrad's residence at Pà Âock Castle. Subjected to constant Prussian raids and counter-raids, Konrad now wanted to stabilize the north of his Duchy of Masovia in this fight over the border area of Cheà Âmno.
Thus in 1226, Konrad, having difficulty with constant raids over his territory, invited the religious military order of the Teutonic Knights to fight the Prussians, as they already had supported the Kingdom of Hungary against the Cuman people in the Transylavanian Burzenland from 1211 to 1225. When they notified Hungary that the Order was, firstly, responsible to the pope, the Knights were expelled by the Hungarian King Andrew II though. Thus, in turn for the Order's service, Grand Master Herman of Salza wanted to have its rights documented beforehand, by a deal with Konrad that was to be confirmed by the Holy Roman Emperor and the Roman Curia.
Emperor Frederick II issued in March 1226 the Golden Bull of Rimini, stating that:
So far, the Knights were not convinced to take the trouble of fighting the Prussians. On the advice of the first Prussian bishop, Christian of Oliva, Konrad instead founded the Loyal Order of Dobrzyà  in 1228. He then called for another Prussian Crusade, and was again defeated. In view of an imminent Prussian invasion, Konrad supposedly signed the Treaty of Kruszwica in 1230, according to which he granted Cheà Âmno Land to the Teutonic Knights and the Order of Dobrzyà Â. By this donation disclaiming any enfeoffment, Konrad established the nucleus of the State of the Teutonic Order. However the document does not exist and it is believed that it was never signed and that the Order most likely forged it. The Knights under the command of Hermann Balk crossed the Vistula river and conquered Cheà Âmno Land, erecting the castle of Toruà  (Thorn) in 1231. In 1234, Pope Gregory IX issued the Golden Bull of Rieti, confirming the prior deals with the Teutonic Knights, stating that the land of the Order was only subject to the Pope, not a fief of anyone. In 1237, the Order's lands were confiscated by Konrad and forced to invest the town of Dobryczin.
Konrad was also entangled in the conflict over the Polish Seniorate Province with his Piast cousin Duke Wà Âadysà Âaw III Spindleshanks of Greater Poland and assumed the title of a Polish High Duke in 1229. However their Silesian relative Duke Henry I the Bearded finally prevailed as High Duke at Kraków in 1232 and confined Konrad's rule again to Masovia. When Henry's son and heir, High Duke Henry II the Pious was killed at the 1241 Battle of Legnica, Konrad once again assumed the senioral title, but had to yield to the claims raised by his nephew Bolesà Âaw V the Chaste, son of his elder brother Leszek, two years later.
Around 1208/1209 Konrad married Agafia of Rus, daughter of Prince Svyatoslav III Igorevich. They had ten children:
Konrad is considered by Poles to be responsible for Teutonic Knights' control of most of the Baltic coastline, undermining Polish authority in the area. King Casimir III of Poland had to accept the rule of the Order in Thorn and Kulm by the 1343 Treaty of Kalisz. After the Thirteen Years' War in the 1466 Second Peace of Thorn, the Polish King Casimir IV Jagiellon gained control over the Cheà Âmno Land as part of Royal Prussia.