The Prime Minister of Great Britain during World War II was Winston Churchill. He served from May 1940 until July 1945, leading the nation through a critical period marked by intense conflict against Nazi Germany. Churchill is known for his inspirational speeches and unwavering determination, rallying British citizens during the Blitz and emphasizing the importance of fighting on. His leadership was pivotal in maintaining Allied morale and coordinating resistance efforts. After the war, he remained a prominent figure in British politics and history, although he lost the subsequent election, demonstrating the complexity of post-war sentiment.