Casimir I, also known as Casimir the Restorer, was a medieval ruler who reigned as the Duke of Poland from 1034 to 1058. He is remembered for his efforts to consolidate and expand the Polish state after a period of fragmentation and external threats. Casimir I is credited with reuniting the territories of Poland and strengthening its political and military power. His reign is considered a pivotal period in the history of Poland, as he laid the foundations for the country's future growth and stability.