The concept of Germany as a distinct region can be traced to Roman commander Julius Caesar, who referred to the unconquered area east of the Rhine as Germania, thus distinguishing it from Gaul (France), which he had conquered. This was a geographic expression, as the area included both Germanic tribes and Celts. The victory of the Germanic tribes in the Battle of the Teutoberg Forest (AD 9) prevented annexation by the Roman Empire. Following the fall of the Roman Empire, the Franks subdued the other West Germanic tribes. When the Frankish Empire was divided among Charlemagne's heirs in 843, the eastern part (now Western Germany) became East Francia, ruled by Louis the German. Henry the Fowler became the first king of Germany in 919. In 962, Henry's son Otto I became the first emperor of what historians refer to as the Holy Roman Empire, the medieval German state.

In the High Middle Ages, the dukes and princes of the empire gained power at the expense of the emperors, who were elected by the princes and crowned by the pope. The northern states became Protestant in the early 16th century, while the southern states remained Catholic. Protestants and Catholics clashed in the Thirty Years' War (1618–1648), which left vast areas depopulated. The peace of Westphalia, which ended the war, is considered the effective end of the Holy Roman Empire and the beginning of the modern nation-state system. Although the Habsburg family continued to use the title "emperor", from this point on their authority was limited to Austria.

After the Napoleonic Wars (1803–1815), Germany was reorganized and the number of states reduced to 39. These states were enrolled in an Austrian-led German Confederation. Nationalist sentiment led to the unsuccessful 1848 March Revolution. A German Empire was created in 1871 under the leadership of Prussian Chancellor Otto von Bismarck. The Reichstag, or elected parliament, had only a limited role in the imperial government. Unification was followed by an industrial revolution. By 1900, Germany's economy was by far the largest in Europe (and second only to the U.S. in the world). Defeated in the First World War (1914–1918), Germany faced territorial losses and war reparations. Emperor Wilhelm II abdicated and democracy was introduced under the Weimar Republic.

The Great Depression, which began in 1929, led to a polarization of German politics and to an upsurge in support for the Communist and Nazi parties. In 1933, the Nazis under Adolf Hitler gained power. The Nazis imposed a totalitarian regime and followed an expansionist foreign policy that led to World War II. After Nazi Germany's defeat, the country was divided into democratic West Germany and communist East Germany. In 1990, East Germany was reunited with West Germany. In recent years, Germany has become increasingly integrated into the European Union, notably with the "Europe 1992" effort to create a unified market and adoption of the euro, a Europe-wide currency, in 2002.