West Germany (in German informally Westdeutschland) was the common English name for the Federal Republic of Germany (in German Bundesrepublik Deutschland), from its founding in May 1949 to October 1990, before the five states of the former German Democratic Republic (GDR, informally East Germany) acceded with effect on 3 October 1990. Since then, the current 16-state Federal Republic of Germany is simply called Germany.

During the Cold War period, after two separate German states and two special territories (the Saarland and Berlin) had been established in Allied Occupation Zones, the Federal Republic had claimed exclusive mandate for all of Germany, as well as considering itself a democratically re-organized German Reich on the grounds that the East German government was not democratically elected and thus not legitimate. Amongst many other consequences, this meant accepting responsibilities for events in the war.

In 1957, the Saarland acceded. The Federal Republic of Germany continued to exist after the process called German reunification, apart from encompassing also the territories of East Germany in addition to the territory of West Germany, area and population getting enlarged by approximately 25% in this process. The accession barely affected the everyday life of the 60 million West Germans, as united Germany continued all of former West Germany's earlier policies, retaining its membership in international organisations as well as its affiliation to Western alliances like EU and NATO.

The foundation for the influential position held by Germany today was laid during the economic Wirtschaftswunder of the 1950s, when West Germany rose from the massive destruction wrought by World War II to become home to the world's fourth largest economies again. The first chancellor Konrad Adenauer, who remained in office until 1963, had not only selected his home town Bonn as provisional capital (thus the era is also called die Bonner Republik—the Bonn Republic ), but also had cemented a full alignment with the West rather than experimenting with a third, neutral way. He not only secured membership in NATO, but was also a founder of cooperations which today have developed into the European Union. By the time of the establishment of the G6/G8 in 1975, there was no question that the Federal Republic of Germany was to be a member in that organization as well.

Western Germany (Westdeutschland) is mainly used as a geographic term.