Piast Dynasty, first ruling family of Poland. According to a 12th-century legend, when Prince Popiel of Gnesen (now Gniezno) died, in the second half of the 9th century, he was succeeded by Siemowit, the son of the prince’s plowman, Piast, thus founding a dynasty that ruled the Polish lands until 1370. (The name Piast was not applied to the dynasty until the 17th century.) By 963 Mieszko I (reigned c. 963–992), probably the fourth prince of the Piast line, was ruling a highly developed, if somewhat isolated, political community in the territories later known as Great Poland and possibly also in Mazovia. Mieszko brought his state into closer association with western Europe, converted it to Christianity (966), and expanded it to include Pomerania (Polish Pomorze) on the Baltic Sea (967–990) as well as Silesia and Little Poland (989–992). His son Bolesław I the Brave (reigned 992–1025) continued the country’s expansion, strengthened its internal administration and church organization, and was crowned its king shortly before his death.
A period of decline then set in during the reigns of Bolesław’s successors—Mieszko II Lambert (1025–34), Bezprym (1031–32), Casimir I the Restorer (1034–37, 1038/39–58), Bolesław II the Bold (1058–79), and Władysław I Herman (1079–1102). The Piast princes lost their title of king (although Bolesław II held it briefly, from 1076 to 1079); they allowed the authority of the central government to diminish in favour of the power of the regional nobility, and they engaged the state in numerous struggles that resulted in a territorial loss. Only after Bolesław III the Wry-Mouthed (reigned 1102–38) succeeded to the throne and exiled his brother and coruler Zbigniew (1107) did Poland’s boundaries reach those of Mieszko I’s domain (by 1125). But Bolesław failed to regain the title of king as well as to reverse the decentralizing tendencies that were undermining the unity of his state. Therefore, in order to avoid future internal conflict based on regional rivalry and to retain unity among the Piast lands, Bolesław divided Poland among his sons. Each of the territorial subdivisions—defined by 1166 as Silesia, Great Poland, Mazovia, and Sandomir—was to be held as the hereditary domain of one of Bolesław’s sons. The senior member of the entire dynasty was also to acquire temporary possession of Kraków and Pomerania and rule as grand prince over the entire loosely federated state of Poland.
The new arrangement, however, stimulated more divisiveness; the power of the grand prince of Kraków declined after the reign of Casimir II the Just (1177–94). For the next 150 years Poland suffered from increasing disunity and disintegration, aggravated by dynastic struggles and civil wars, foreign intervention and invasion, and the secession and conquest of its border regions.
Nevertheless, throughout this period of political division, the Piast lands retained their common church structure, language, and economy, all of which provided a basis for various princes to try to reunify the Polish kingdom. The first attempts failed; they were made by the Silesian princes Henry I and Henry II in the 1230s and by the prince of Great Poland Przemysł II (reigned at Kraków 1279–95 and as king of Poland 1295–96). But after Wenceslas II (Polish Wacław) of Bohemia gained control of two-thirds of the Polish lands and became king of Poland (1300–05), Władysław I the Short (Łokietek), a grandson of Conrad I of Mazovia, gained support from the gentry, the leading clergy, and some members of the upper nobility and won control of Sandomir and Kraków (by 1306); with the aid of Hungary and the pope, he became the ruler of Great Poland and also king of Poland (1320). Władysław I strengthened Poland substantially by forming close alliances, through the marriages of his children, with both Hungary and Lithuania.
His son Casimir III the Great assumed the throne of the restored Polish kingdom (1333) and further improved its position by coming to terms with his two major enemies, Bohemia and the Teutonic Knights. He accepted Poland’s loss of Silesia and Pomerania, annexed Galicia, and regained Mazovia (1349). Casimir also consolidated his rule over the state by improving its economy and military and civil administrations, codifying the laws of Great and Little Poland, and founding a university at Kraków (1364).
Casimir’s death, however, brought an end to his line of the Piast dynasty. Having developed the newly reunified Piast lands into a stable, prosperous, and powerful nation, he left his kingdom to his sister’s son, Louis I of Hungary. After ruling from 1370 to 1382, Louis was succeeded by his daughter Jadwiga and her husband Jogaila (Władysław II Jagiełło), the grand duke of Lithuania. This succession marked the founding of the Jagiellon dynasty in Poland.