Bolesław the Brave (Polish: Bolesław Chrobry Polish , Czech: Boleslav Chrabrý; 967 – 17 June 1025), less often known as Bolesław the Great (Polish: Bolesław Wielki), was Duke of Poland from 992 to 1025, and the first King of Poland in 1025. He was also Duke of Bohemia between 1003 and 1004 as Boleslaus IV.

He was the son of Mieszko I of Poland by his wife, Dobrawa of Bohemia. According to a scholarly theory, Bolesław ruled Lesser Poland already during the last years of his father's reign. Mieszko I, who died in 992, divided Poland among his sons, but Bolesław expelled his father's last wife, Oda of Haldensleben, and his half-brothers and reunited Poland between 992 and 995.

Bolesław supported the missionary goals of Bishop Adalbert of Prague and Bruno of Querfurt. The martyrdom of Adalbert in 997 and his imminent canonization were used to consolidate Poland's autonomy from the Holy Roman Empire. This perhaps happened most clearly during the Congress of Gniezno (11 March 1000), which resulted in the establishment of a Polish church structure with a Metropolitan See at Gniezno. This See was independent of the German Archbishopric of Magdeburg, which had tried to claim jurisdiction over the Polish church. Following the Congress of Gniezno, bishoprics were also established in Kraków, Wrocław, and Kołobrzeg, and Bolesław formally repudiated paying tribute to the Holy Roman Empire. Following the death of Holy Roman Emperor Otto III in 1002, Bolesław fought a series of wars against the Holy Roman Empire and Otto's cousin and heir, Henry II, ending in the Peace of Bautzen (1018). In the summer of 1018, in one of his expeditions, Bolesław I captured Kiev, where he installed his son-in-law Sviatopolk I as ruler. According to legend, Bolesław chipped his sword when striking Kiev's Golden Gate. Later, in honor of this legend, a sword called Szczerbiec ("Jagged Sword") would become the coronation sword of Poland's kings.

Bolesław I was a remarkable politician, strategist, and statesman. He not only turned Poland into a country comparable to older western monarchies, but he raised it to the front rank of European states. Bolesław conducted successful military campaigns in the west, south and east. He consolidated Polish lands and conquered territories outside the borders of modern-day Poland, including Slovakia, Moravia, Red Ruthenia, Meissen, Lusatia, and Bohemia. He was a powerful mediator in Central European affairs. Finally, as the culmination of his reign, in 1025 he had himself crowned King of Poland. He was the first Polish ruler to receive the title of rex (Latin: "king").

He was an able administrator who established the "Prince's Law" and built many forts, churches, monasteries and bridges. He introduced the first Polish monetary unit, the grzywna, divided into 240 denarii, and minted his own coinage. Bolesław I is widely considered one of Poland's most capable and accomplished Piast rulers.