Konrad I of Masovia

Konrad I (c. 1187–1247), youngest son of Casimir II the Just, was duke of Masovia from 1194 and Kuyavia from 1205. In 1205 he and his brother Leszek the White defeated Roman the Great of Galicia–Volhynia at Zawichost, where Roman was killed. His repeated campaigns against pagan Prussia failed amid border raids.

In 1226 he invited the Teutonic Order to conquer Chełmno Land and subdue the Prussians, and the order's rights were confirmed when Frederick II issued the Golden Bull of Rimini. He seized the Kraków seniorate as high duke in 1229–1232 and again in 1241–1243, and died in 1247.