Mainz is the capital and largest city of Rhineland-Palatinate, Germany. The city is located on the Rhine river at its confluence with the Main river, opposite Wiesbaden on the border with Hesse. Mainz is an independent city with a population of 206,628 and forms part of the Frankfurt Rhine-Main Metropolitan Region. It was the site of a Celtic settlement where the Romans established (14-9 BCE) a military camp known as Mogontiacum (Moguntiacum), after the Celtic god Mogo. Once the episcopal seat of the influential Prince-Electors, the "civilized" origins of Mainz date back to around 38 BC, when the Romans built a citadel here. The city's location at the confluence of the Rhine and the Main is ideal for trade, something reflected by the artifacts kept in the Landesmuseum, that show there have been settlements here since 300,000 BC.  The town that developed became the capital of Germania Superior until the Romans abandoned the area about 451 CE. In the 6th century there arose a new town, which became a bishopric (747) and the ecclesiastical center of Germany under St. Boniface and an archbishopric (775-780).   

The community grew rapidly, gaining certain rights of self-government in 1118 and becoming a free imperial city in 1244. As 'Golden Mainz,' it was the center of a powerful league of Rhenish towns in 1254. The archbishops became chancellors and electors of the Holy Roman Empire in the 14th century.

Mainz was founded by the Romans in the 1st Century BC during the Classical antiquity era, serving as a military fortress on the northernmost frontier of the Roman Empire and as the provincial capital of Germania Superior. Mainz became an important city in the 8th Century AD as part of the Holy Roman Empire, becoming the capital of the Electorate of Mainz and seat of the Archbishop-Elector of Mainz, the Primate of Germany. Mainz is famous as the home of Johannes Gutenberg, the inventor of the movable-type printing press, who in the early 1450s manufactured his first books in the city, including the Gutenberg Bible. Following an economic decline, climaxed by warfare between two rival archbishops in 1462, its citizens were deprived of their privileges. Many craftsmen were driven into exile, spreading the knowledge of the art of printing.

Although the city was occupied by the Swedes and the French during the Thirty Years' War, it remained a flourishing commercial and cultural center until it was reoccupied by the French in 1792. It was successfully besieged by the Prussians and Austrians (1793) but was ceded to France by the Treaties of Campo Formio (1797) and Lunéville (1801). The French suppressed the archbishopric (replaced by a bishopric in 1801) and secularized the electorate in 1803. French dominance ended in 1816, when the city passed to Hesse-Darmstadt and became the capital of the newly formed Rhenish-Hesse province. It was a fortress of the German Confederation and later of the German Empire. Mainz was occupied by French troops after World Wars I and II. About four-fifths of the inner city was destroyed during World War II, but reconstruction was rapid and extensive.   Mainz was heavily damaged during World War II, with more than 30 air raids destroying about 80 percent of the city's center, including most of the historic buildings.

Today, Mainz is a transport hub and a center of wine production.  Mainz is known for its old town, with half-timbered houses and medieval market squares. In the center, the Marktbrunnen is a Renaissance fountain with red columns. Nearby, a distinctive octagonal tower tops the Romanesque Mainz Cathedral, built of deep red sandstone. The Gutenberg Museum honors the inventor of the printing press with exhibits, including 2 of his original bibles.  Mainz is one of the centers of the German wine economy as a center for wine trade and the seat of the state's wine minister. Due to the importance and history of the wine industry for the federal state, Rhineland-Palatinate is the only state to have such a department.  Since 2008, the city is also member of the Great Wine Capitals Global Network (GWC), an association of well-known wineculture-cities of the world. Many wine traders also work in the town. The sparkling wine producer Kupferberg produced in Mainz-Hechtsheim and even Henkell - now located on the other side of the river Rhine — had been founded once in Mainz. The famous Blue Nun, one of the first branded wines, had been marketed by the family Sichel.  Mainz had been a wine growing region since Roman times and the image of the wine town Mainz is fostered by the tourist center. The Haus des Deutschen Weines (English: House of German Wine), is located in beside the theater. The Mainzer Weinmarkt (wine market) is one of the great wine fairs in Germany.

Some remains of Roman times survive, and relics are housed in the Roman-Germanic Central Museum. St. Martin's Cathedral (also known as Mainz Cathedral), originally erected 975-1009, has been repeatedly rebuilt, acquiring accretions of many later styles in addition to its original Romanesque architecture. Henry II, Conrad II, and Frederick II were crowned there. Other historic landmarks include the churches of St. Ignatius (1763–74), St. Stephen (1257–1328), and St. Peter (1748–56) and the Renaissance Electoral Palace (1627–78), all renovated after World War II.

A university city from 1477 until 1816, Mainz regained this status with the establishment in 1946 of Johannes Gutenberg University, with which special institutes are associated, including the Institute for Economic Research. Also in the city are the Max Planck Institutes for Chemistry and for Polymer Research and the Academy of Sciences and Literature. Gutenberg is also honored by the Gutenberg Monument (1837), the Gutenberg Museum, and the headquarters building of the International Gutenberg Society. There are museums of art, history, and natural history, as well as a diocesan museum. Mainz is the site of an annual fair and pre-Lenten festivals.