Konrad I of Masovia

Konrad of Mazovia (1187 - 1247) was Duke of Mazovia, son of Casimir II of Poland ("the Just") and Helen, princess of Moravia. After his father's death in 1194, he was brought up by his mother and in 1202 he received Mazovia and Kujawy. He married the Russian princess Agafia. In 1228 he brought the military order of Teutonic Knights to Prussia and granted lands to Teutonic Order and Bracia Dobrzynscy.

He is perhaps best remembered as the infamous and gullible ruler who invited the Teutonic Knights to Poland. Over the coming centuries this would lead to the famous battle of Grunwald and eventual loss of Pomorze and Prusy territories by Poland.