德意志联邦共和国，简称西德或联邦德国（德语：Bundesrepublik Deutschland，缩写BRD）建立于1949年5月23日，其初期范围包括二战后由英国、美国和法国所占领的德国领土。在1990年两德统一还都至柏林之前，西德的首都是设置于波恩。而除了德国西部的领土外，东德境内、德国原本的首都柏林市区西半部在当时也属于西德领土。西柏林因为由东德领土包围，是一个飞地。
在两德统一之后，德意志民主共和国（东德）消失，由德意志联邦共和国作为统一后的存续单位。
历史
第二次世界大战纳粹德国战败，根据战时波茨坦会议中英、美、法、苏四国的秘约，决定在德国战败后将其一分为四分别由四个战胜国占领，并且合组一个最高管理单位同盟管理议会（Allied Control Council，ACC）来治理德国事务。但由于理念上的差异，在战后以美国为主的西方阵营与以苏联为主的共产阵营逐渐疏远，1948年3月时，美、英、法三国在伦敦举行会议，初步决议要将三国所分别管理的德国领土合并，组成一个德国西部的政权，针对这点苏联方面作出反制，首先是退出ACC，并进而宣布着手设立一个东德政权的计划。
但直接导致东西德分离的导火线，则是发生在1948年6月20日，西方占领区境内的货币重整计划。当时西方三国占领区内原本分别发行的货币整合为一，但却排除苏联占领区，发行了所谓的西德马克，而苏联占领区也在短短三日后发行了东德马克，俨然象征东西德正式分离。东西德分离后，东德方面曾在1948年中开始，对使用西德马克的西柏林地区进行封锁，为期11个月，希望透过此举达到完全控制整个柏林地区的目的，但却在西方国家持续以空运方式所进行的柏林空运之支援下没有实现。在柏林封锁解除（1949年5月12日）后没多久的5月23日，西德（德意志联邦共和国）宣布正式成立。而东德方面也在同年的10月7日宣布正式成立以德意志社会主义统一党（缩写：SED）一党专政的社会主义共和政体。
西德于1955年5月8日加入北约，相对的，由苏联扶植、共党主政的东德（德意志民主共和国）则加入了华沙条约组织，使得东西德间的交界成为两大对垒阵营的最前线，冷战的焦点。
在1989年11月9日柏林墙倒塌后，东德领土于1990年10月3日正式并入西德，德意志联邦共和国从此覆盖德国全境，德国统一成一个国家。1991年3月15日，四个占领国正式放弃对其的占领权。因此除了视为是一个分裂状态下的独立国家之外，西德也可被视为是当代德国（德意志联邦共和国）的一段历史时期。
West Germany (German: Westdeutschland) is a common English name for the period of the Federal Republic of Germany (German: Bundesrepublik Deutschland, BRD) between the adoption of the new constitution in May 1949 to German reunification in October 1990, when the (East) German Democratic Republic was dissolved and the five states on its territory joined the Federal Republic of Germany, ending the more than 40-year division of Germany and Berlin. From the 1990 reunification onwards, the enlarged Federal Republic of Germany with sixteen states has been exclusively known as Germany in common usage.
The Federal Republic of Germany was organized from the initially 12 states formed in the three Western Zones or Allied Zones of occupation held by the United States, the United Kingdom, and France. Bonn was selected as its provisional capital city, rather than the enclave of West Berlin which had a special status, but practically was part of the Federal Republic. The fourth Allied occupation zone or East Zone (Ostzone) was held by the Soviet Union. The parts east of the Oder-Neisse were de facto annexed by the Soviet Union and Communist Poland, the remaining central part around Berlin became the communist German Democratic Republic, GDR (in German: Deutsche Demokratische Republik, DDR) with its de facto capital East Berlin. As a result, the remaining Western Germany had a territory about half the size of its previous democratic-capitalist antecessor, the interwar Weimar Republic.
At the onset of the Cold War, Europe and Germany were divided among the Western and Eastern blocs. Germany was de facto divided into two countries, plus 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 re-organized German Reich on the grounds that the GDR government was not democratically elected, but was installed by a foreign occupying power and thus not legitimate. The number of federal states changed in the 1950s, when three south western states merged to form a single Baden-Württemberg in 1952, and when the Saarland joined the Federal Republic of Germany in 1957. In addition to the official ten states, West Berlin was considered an unofficial de facto eleventh state. While legally not part of the Federal Republic of Germany, as it was under four-power occupation, West Berlin was represented directly or indirectly in federal institutions.
Relations with the Soviet bloc improved during the era of Ostpolitik in the 1970s, and the two German states recognized the existence of each other. De jure West Germany formally maintained the exclusive mandate: it recognized the GDR as a de facto government still within a single German nation that in turn is represented de jure by the West German state only, while East Germany recognized the existence of two German countries de jure, and the West as both de facto and de jure foreign country.
The foundation for the influential position held by Germany today was laid during the Wirtschaftswunder (economic miracle) of the 1950s, when West Germany rose from the massive 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 he 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.
When the system of state socialism collapsed in East Germany and the wider Central and Eastern Europe in 1989–1990, symbolized by the opening of the Berlin Wall, there was a rapid move towards German reunification. East Germany voted to dissolve itself and accede to the Federal Republic in 1990. Its postwar five states (Länder) were reconstituted, and along with reunited Berlin, which ended its special status and formed an additional Land, they formally joined the Federal Republic of Germany on 3 October 1990, raising the number of states from 10 to 16. The expanded Federal Republic of Germany, now exclusively known as simply Germany in the English language, retained its political culture, and it continues the memberships in international organizations, as well as its Western foreign policy alignment and affiliation to Western alliances like the European Union and NATO. The enlarged Federal Republic of Germany is the continuation of, and not a successor to, the (West German) Federal Republic of Germany with fewer states until 1990.
Western Germany (Westdeutschland or westliches Deutschland), where it is not a synonym for "West Germany", is mainly used as a geographic term referring vaguely to the Rhineland, a usage which dates back to before the Cold War. Citizens of the Federal Republic called their country Federal Republic, FR Germany or simply Germany. In the early years, the GDR termed the Federal Republic Westdeutschland, later the FRG (BRD). This abbreviation was strongly disliked by the West Germans as GDR jargon.