The British Prime Minister known for his role during World War II was Winston Churchill. Churchill served as Prime Minister from 1940 to 1945 and became an iconic leader known for his defiant stance against Nazi Germany. His speeches and radio broadcasts inspired British resilience during the darkest days of the war. Churchill famously rallied the nation with promises of "blood, toil, tears, and sweat," calling for unity and determination. His leadership, strategic foresight, and alliances with the United States and the Soviet Union played significant roles in the Allies' eventual victory.