Mainz (German: [mants] (listen)) is the capital and largest city of Rhineland-Palatinate (German: Rheinland-Pfalz), Germany.

Mainz is located on the left-bank of the Rhine, opposite where the Main joins the Rhine. Downstream of this confluence, the Rhine flows to the north-west, with Mainz on the left-bank, and Wiesbaden, the capital of the neighbouring state Hesse, on the right-bank.

Mainz is an independent city with a population of 218,578 (as of 2019) and forms part of the Frankfurt Rhine-Main Metropolitan Region.Mainz was founded by the Romans in the 1st century BC as a military fortress on the northernmost frontier of the empire and provincial capital of Germania Superior. Mainz became an important city in the 8th century AD as part of the Holy Roman Empire, capital of the Electorate of Mainz and seat of the Archbishop-Elector of Mainz, the Primate of Germany. Mainz is famous as the birthplace of Johannes Gutenberg, the inventor of a movable-type printing press, who in the early 1450s manufactured his first books in the city, including the Gutenberg Bible. Mainz was heavily damaged in World War II; more than 30 air raids destroyed most of the historic buildings.

Mainz is notable as a transport hub, for wine production, and for its many rebuilt historic buildings. One of the ShUM-cities, Mainz and its Jewish cemetery is part of the UNESCO World Heritage Site.

The Kingdom of Prussia (German: Königreich Preußen) was a German kingdom that constituted the state of Prussia between 1701 and 1918. It was the driving force behind the unification of Germany in 1871 and was the leading state of the German Empire until its dissolution in 1918. Although it took its name from the region called Prussia, it was based in the Margraviate of Brandenburg. Its capital was Berlin.The kings of Prussia were from the House of Hohenzollern. Brandenburg-Prussia, predecessor of the kingdom, became a military power under Frederick William, Elector of Brandenburg, known as "The Great Elector". As a kingdom, Prussia continued its rise to power, especially during the reign of Frederick II, more commonly known as Frederick the Great, who was the third son of Frederick William I. Frederick the Great was instrumental in starting the Seven Years' War (1756–63), holding his own against Austria, Russia, France and Sweden and establishing Prussia's role in the German states, as well as establishing the country as a European great power. After the might of Prussia was revealed, it was considered as a major power among the German states. Throughout the next hundred years Prussia went on to win many battles, and many wars. Because of its power, Prussia continuously tried to unify all the German states (excluding the German cantons in Switzerland) under its rule, and whether Austria would be included in such a unified German domain was an ongoing question.

After the Napoleonic Wars led to the creation of the German Confederation, the issue of unifying the German states caused a number of revolutions throughout the German states, with all states wanting to have their own constitution. Attempts to create a federation remained unsuccessful and the German Confederation collapsed in 1866 when war ensued between its two most powerful member states, Prussia and Austria. The North German Confederation, which lasted from 1867 to 1871, created a closer union between the Prussian-aligned states while Austria and most of Southern Germany remained independent. The North German Confederation was seen as more of an alliance of military strength in the aftermath of the Austro-Prussian War but many of its laws were later used in the German Empire. The German Empire lasted from 1871 to 1918 with the successful unification of all the German states aside from Austria under Prussian hegemony; this was due to the defeat of Napoleon III in the Franco-Prussian War of 1870–71. The war united all the German states against a common enemy, and with the victory came an overwhelming wave of nationalism which changed the opinions of some of those who had been against unification. In 1871, Germany unified into a single country, minus Austria and Switzerland, with Prussia the dominant power.Prussia is considered the legal predecessor of the unified German Reich (1871–1945) and as such a direct ancestor of today's Federal Republic of Germany. The formal abolition of Prussia, carried out on 25 February 1947 by the Allied Control Council, referred to a tradition of the kingdom as a bearer of militarism and reaction, and made way for the current setup of the German states. However, the Free State of Prussia (Freistaat Preußen), which followed the abolition of the Kingdom of Prussia in the aftermath of World War I, was a major democratic force in Weimar Germany until the nationalist coup of 1932 known as the Preußenschlag. The Kingdom left a significant cultural legacy, today notably promoted by the Prussian Cultural Heritage Foundation (Stiftung Preußischer Kulturbesitz (SPK)), which has become one of the largest cultural organisations in the world.