The Piast dynasty was the first historical ruling dynasty of Poland. It began with the semi-legendary Piast Kołodziej (Piast the Wheelwright). The first historical ruler was Prince Mieszko I (tenth century). The Piasts' royal rule in Poland ended in 1370 with the death of king Casimir the Great. Branches of the Piast dynasty continued to rule in the Duchy of Masovia and in the duchies of Silesia after 1370, until the last male Silesian Piast died in 1675. The Piasts intermarried with several noble lines of Europe, and possessed numerous titles, some within the Holy Roman Empire.

Although the early dukes and kings of Poland regarded themselves as descendants of Piast, the term "Piast Dynasty" originated in the 17th century: historians working for a number of rulers who governed duchies in Silesia invented the concept. In a historical book the term was first used by Adam Naruszewicz in his History of the Polish Nation (1780–86).

Piast Kołodziej (Piast the Wheelwright) was the legendary founder of the Piast dynasty. His name is first mentioned in the Cronicae et gesta ducum sive principum Polonorum of Gallus Anonymus, written c. 1113. The last Silesian Piast George William of Liegnitz-Brieg-Wohlau (Brzeg and Legnica) died in 1675, although numerous families link their genealogy to the Piasts. His son August Freiherr von Liegnitz (1628) and Graf von Liegnitz (1664), the last legitimate male, died in 1679 and the last male through illegitimate line Ferdinand II Freiherr von und zu Hohenstein of the Dukes of Teschen died in 1706. Another illegitimate branch, the Grafen von Karlinsmarck zu Friedland und Strehlitz, born of Bernhard of Silesia-Oppeln, duke of Falkenberg, by a lady Karlinska of Karlowice, died out at the beginning of the 19th century in a French family.

Genghis Khan (/ˈɡɛŋɡɪs ˈkɑːn/ or /ˈdʒɛŋɡɪs ˈkɑːn/,Mongol: [tʃiŋɡɪs xaːŋ] ( listen); 1162? – August 1227), born Temujin, was the founder and Great Khan (emperor) of the Mongol Empire, which became the largest contiguous empire in history after his death.

He came to power by uniting many of the nomadic tribes of northeast Asia. After founding the Mongol Empire and being proclaimed "Genghis Khan", he started the Mongol invasions that resulted in the conquest of most of Eurasia. These included raids or invasions of the Kara-Khitan Khanate, Caucasus, Khwarezmid Empire, Western Xia and Jin dynasties. These campaigns were often accompanied by wholesale massacres of the civilian populations – especially in Khwarezmia. By the end of his life, the Mongol Empire occupied a substantial portion of Central Asia and China.

Before Genghis Khan died, he assigned Ögedei Khan as his successor and split his empire into khanates among his sons and grandsons. He died in 1227 after defeating the Western Xia. He was buried in an unmarked grave somewhere in Mongolia at an unknown location. His descendants went on to stretch the Mongol Empire across most of Eurasia by conquering or creating vassal states out of all of modern-day China, Korea, the Caucasus, Central Asian countries, and substantial portions of modern Eastern Europe, Russia and the Middle East. Many of these invasions resulted in the large-scale slaughter of local populations, which have given Genghis Khan and his empire a fearsome reputation in local histories.