The history of Poland spans over a thousand years, from medieval tribes, Christianization and monarchy; through Poland's Golden Age, expansionism and becoming one of the largest European powers; to its collapse and partitions, two world wars, communism, and the restoration of democracy.
The roots of Polish history can be traced to ancient times, when the territory of present-day Poland was inhabited by diverse ethnic groups, including Celts, Scythians, Sarmatians, Slavs, Balts and Germanic peoples. However, it was the West Slavic Lechites, the closest ancestors of ethnic Poles, who established permanent settlements during the Early Middle Ages. The Lechitic Western Polans, a tribe whose name denotes "people living in open fields", dominated the region and gave Poland - which lies in the North-Central European Plain - its name. The first ruling dynasty, the Piasts, emerged in the 10th century AD. Duke Mieszko I, regarded as the creator of Polish statehood, adopted Western Christianity in 966 CE. Mieszko's dominion was formally reconstituted as a medieval kingdom in 1025 by his son Bolesław I the Brave, known for his military expansions. The most successful and the last Piast monarch, Casimir III the Great, presided over a period of economic prosperity and territorial aggrandizement before his death in 1370 without male heirs.