Western Europe is the western region of Europe. The region's extent varies depending on context. The concept of "the West" appeared in Europe in juxtaposition to "the East" and originally applied to the Western half of the ancient Mediterranean world, the Latin West of the Roman Empire, and "Western Christendom". Beginning with the Renaissance and the Age of Discovery, roughly from the 15th century, the concept of Europe as "the West" slowly became distinguished from and eventually replaced the dominant use of "Christendom" as the preferred endonym within the area. By the Age of Enlightenment and the Industrial Revolution, the concepts of "Eastern Europe" and "Western Europe" were more regularly used. The distinctiveness of Western Europe became most apparent during the Cold War, when Europe was divided for 40 years by the Iron Curtain into the Western Bloc and Eastern Bloc, each characterised by distinct political and economical systems.

Prior to the Roman conquest, a large part of Western Europe had adopted the newly developed La Tène culture. As the Roman domain expanded, a cultural and linguistic division appeared between the mainly Greek-speaking eastern provinces, which had formed the highly urbanised Hellenistic civilisation, and the western territories, which in contrast 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 Western Roman Empire and the Eastern Roman Empire controlled the two divergent regions between the 3rd and the 5th centuries.

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 the Greek or Byzantine Empire, survived and even thrived for another 1000 years. The rise of the Carolingian Empire in the west, and in particular the Great Schism between Eastern Orthodoxy and Roman Catholicism, enhanced the cultural and religious distinctiveness between Eastern and Western Europe.

After 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 Carolingian Empire), the division between Roman Catholic and Protestant became more important in Europe than that with Eastern Orthodoxy.

In East Asia, Western Europe was historically known as taixi in China and taisei in Japan, which literally translates as the "Far West". The term Far West became synonymous with Western Europe in China during the Ming dynasty. The Italian Jesuit priest Matteo Ricci was one of the first writers in China to use the Far West as an Asian counterpart to the European concept of the Far East. In Ricci's writings, Ricci referred to himself as "Matteo of the Far West". The term was still in use in the late 19th and early 20th centuries.

Christianity is the largest religion in Western Europe. According to a 2018 study by the Pew Research Center, 71.0% of Western Europeans identified as Christians.

In 1054, the East–West Schism divided Christianity into Western Christianity and Eastern Christianity. This split Europe in two, with Western Europe primarily under the Catholic Church, and much of Eastern Europe under the Eastern Orthodox Church. Ever since the Reformation in the 16th century, Protestantism has also been a major denomination in Europe, mostly in the West.

During the four decades of the Cold War, the definition of East and West was simplified by the existence of the Eastern Bloc. A number of historians and social scientists view the Cold War definition of Western and Eastern Europe as outdated or relegating.