The leader of the United Kingdom during World War I was Prime Minister David Lloyd George. Serving as Prime Minister from 1916 to 1922, Lloyd George played a critical role in leading Britain through the later stages of the war and in the post-war period. He was known for his dynamic leadership style and for uniting the country during a time of national crisis. Lloyd George was a key figure in the Paris Peace Conference following the war, advocating for a Treaty of Versailles that would address the causes of the conflict. His policies and decisions significantly influenced Britain's role in international affairs during and after the war.