Western Europe refers to the countries in the westernmost half of Europe.

The term has geographic, political, and cultural aspects. Since the end of World War II, the term has been used to describe the high-income developed countries of western Europe, characterized by democratic political systems, mixed economies combining the free market with aspects of the welfare state, alliance with the United States, and membership in NATO.

Classical antiquity and medieval origins

As Roman domain expanded a cultural and linguistic division appeared between the mainly Greek-speaking eastern provinces which had formed the highly urbanized Hellenistic civilization. In contrast, the western territories largely adopted the Latin language. This cultural and linguistic division was eventually reinforced by the later political east-west division of the Roman Empire

The division between these two was enhanced during Late Antiquity and the Middle Ages by a number of events. The Western Roman Empire collapsed starting the Early Middle Ages. By contrast, the Eastern Roman Empire, mostly known as Byzantine Empire, managed to survive and even to thrive for another 1000 years. The rise of the Frankish Empire in the west, and in particular the Great Schism that formally divided Eastern Orthodoxy and Roman Catholicism, enhanced the cultural and religious distinctiveness between Eastern and Western Europe.

The conquest of the Byzantine Empire, center of the Eastern Orthodox Church, by the Muslim Ottoman Empire in the 15th century, and the gradual fragmentation of the Holy Roman Empire (which had replaced the Frankish Empire) led to a change of the importance of Roman Catholic/Protestant vs. Eastern Orthodox concept in Europe.

Historical events like the Renaissance, the Protestant Reformation by Martin Luther and the Counter-Reformation of the Catholic Church, the Age of Enlightenment, the French Revolution and the Industrial Revolution are considered to be common during the final stages of World War II the future of Europe was decided between the Allies in the 1945 Yalta Conference, between the British Prime Minister Winston Churchill, U.S. President Franklin Delano Roosevelt, and the Premier of the Soviet Union, Joseph Stalin.

Post-war Europe would be divided into two major spheres: the West, influenced by the United States, and the Eastern Bloc, dominated by the Soviet Union. With the onset of the Cold War, Europe was divided by the Iron Curtain.

This term had been used during World War II by German Propaganda Minister Joseph Goebbels and later Count Lutz Schwerin von Krosigk in the last days of the war; however, its use was hugely popularised by Winston Churchill, who used it in his famous "Sinews of Peace" address March 5, 1946 at Westminster College in Fulton, Missouri:

Although some countries were officially neutral, they were classified according to the nature of their political and economical systems. This division has largely defined the popular perception and understanding of Western Europe and its borders with Eastern Europe till this day.