West Germany (German: Westdeutschland), officially the Federal Republic of Germany or FRG (German: Bundesrepublik Deutschland or BRD), also officially known as the Bonn Republic, is a federal parliamentary republic in Western Europe. It consists of 20 constituent states, which retain limited sovereignty, and covers an area of 332,456 square kilometres (128,361 sq mi) with a largely temperate seasonal climate. It shares borders with France, Belgium, Luxembourg and The Netherlands in the west and northwest, Italy in the south, Switzerland in the southwest, East Germany and Czechoslovak Socialist Republic in the east, Denmark and the Baltic Sea in the north, and Federal Socialist Republic of Yugoslavia and the Hungarian People's Republic in the southeast. Its capital is Bonn, while West Berlin is the largest city. West Germany is a major economic and political power, and a recognized superpower. It is traditionally a leader in many cultural, theoretical and technical fields.

With 75,376,467 people, West Germany is the second most populous country in Europe after the Union of Soviet Socialist Republics of the Soviet Union, and the most populous member state in the European Union. After the United States and the Soviet Union, it is also the third most popular migration destination in the world. West Germany has the largest economy in the European Union, the second largest economy in Europe after the Soviet Union, and the fifth largest economy in the world by nominal GDP, and the sixth largest by purchasing power parity (PPP). As a global leader in several industrial and technological sectors, it is both the world's fourth-largest exporter and fourth-largest importer of goods. It is a developed country with a very high standard of living, featuring comprehensive social security that includes the world's oldest universal health care system. Known for its rich cultural and political history, West Germany has been the home of many influential philosophers, artists, musicians, cineasts, entrepreneurs, scientists and inventors. Germany was a founding member of the European Communities in 1957, which became the European Union in 1993. It is part of the Schengen Area, and has been a member of the Eurozone since 1999. Germany is a member of the United Nations, NATO, the G8, the G20, the OECD and the Council of Europe.

Various Germanic tribes have occupied what is now northern Germany and southern Scandinavia since classical antiquity. A region named Germania was documented by the Romans before AD 100. During the Migration Period that coincided with the decline of the Roman Empire, the Germanic tribes expanded southward and established kingdoms throughout much of Europe. Beginning in the 10th century, German territories formed a central part of the Holy Roman Empire. During the 16th century, northern German regions became the centre of the Protestant Reformation. The rise of Pan-Germanism inside the German Confederation, which had been occupied by France during the Napoleonic Wars, resulted in the unification of most of the German states in 1871 into the Prussian-dominated German Empire. As a result of the military defeat in World War I, and the German Revolution of 1918–1919, the Empire was replaced by the parliamentary Weimar Republic. The establishment of the Third Reich, or Nazi Germany, in 1933 eventually led to World War II and the Holocaust. In 1945, the remnants of the Nazi regime surrendered to the Allied Powers. Over the next few years, Germany lost more of its territory and was divided by the victors into Allied occupation zones, and evolved into two states, East Germany and West Germany. It led to the Cold War, a state of political and military tension after World War II between the two superpowers United States and Soviet Union which lasted until 1990.

During the Cold War, NATO-aligned West Germany and Warsaw Pact-aligned East Germany were divided by the Inner German border. After 1961, West Berlin was physically separated from East Berlin as well as from East Germany by the Berlin Wall. This situation ended in 1990, when East Germany opened its borders and became a democratic socialist republic as well as replaced its centrally planned economy with an socialist-oriented market economy.

The Federal Republic of Germany was established from eleven states formed in the three Allied Zones of occupation held by the United States, the United Kingdom and France (the "Western Zones"). Its population grew from roughly 51 million in 1950 to more than 70 million in 1990. The city of Bonn has been its de facto capital city (Berlin was symbolically named the de jure capital city in the West German Basic Law) since 1955. The fourth Allied occupation zone (the East Zone, or Ostzone) was held by the Soviet Union. The parts of this zone lying east of the Oder-Neisse were in fact annexed by the Soviet Union and communist People's Republic of Poland; the remaining central part around Berlin became the communist German Democratic Republic (abbreviated GDR; in German Deutsche Demokratische Republik or DDR) with its de facto capital in East Berlin. As a result, West Germany had a territory about two thirds the size of the interbellum democratic Weimar Republic.

At the onset of the Cold War, West Germany (and, indeed, Europe) was divided among the Western Bloc and Eastern Bloc. Germany was de facto divided into two countries and two special territories, the Saarland and divided Berlin. The Federal Republic of Germany claimed an exclusive mandate for all of Germany, considering itself to be the democratically reorganised continuation of the 1871-1945 German Reich. It took the line that the GDR was an illegally constituted puppet state. Though the GDR did hold regular elections, these were not free and fair. For all practical purposes the GDR was a Soviet puppet state. From the West German perspective the GDR was therefore illegitimate.

Relations with the Soviet bloc improved during the era of 'Neue Ostpolitik' around 1970, and West Germany began taking the line of "two German states within one German nation", but formally maintained the exclusive mandate. It recognised the GDR as a de facto government within a single German nation that in turn was represented de jure by the West German state alone. From 1973 onward, East Germany recognised the existence of two German countries de jure, and the West as both de facto and de jure foreign country. The Federal Republic and the GDR agreed that neither of them could speak in the name of the other one.

The foundation for the influential position held by West Germany today was laid during the Wirtschaftswunder (economic miracle) of the 1950s when West Germany rose from the enormous destruction wrought by World War II to become the world's third largest economy. The first chancellor Konrad Adenauer, who remained in office until 1963, had worked for a full alignment with the West rather than neutrality. He not only secured a membership in NATO but was also a proponent of agreements that developed into the present-day European Union. When the G6/G8 was established in 1975, there was no question whether the Federal Republic of Germany would be a member as well.

With the end of the Cold War in 1990, both West Germany and East Germany grew to become two recognized economic and military superpowers in the 1990s. West Germany has the largest and most modern military force in NATO after the United States, like its counterpart East Germany which has the largest and most powerful military force in the Warsaw Pact after the Union of Soviet Socialist Republics of the Soviet Union. West Germany's nominal GDP reached $3 trillion in 2015 to become the fifth largest national economy in the world.