The Suebi (or Suebians, also spelled Suevi, Suavi) were a large group of Germanic peoples originally from the Elbe river region in what is now Germany and the Czech Republic. In the early Roman era they included many peoples with their own names such as the Marcomanni, Quadi, Hermunduri, Semnones, and Lombards. New groupings formed later such as the Alamanni and Bavarians and two kingdoms in the Migration Period were simply referred to as Suebian.
Although Tacitus specified that the Suebian group was not an old tribal group itself, the Suebian peoples are associated by Pliny the Elder with the Irminones, a grouping of Germanic peoples who claimed ancestral connections. Tacitus mentions Suebian languages, and a geographical "Suevia".
The Suevians were first mentioned by Julius Caesar in connection with the invasion of Gaul by the Germanic king Ariovistus during the Gallic Wars. Unlike Tacitus he described them as a single people, distinct from the Marcomanni, within the larger Germanic category who he saw as a growing threat to Gaul and Italy in the first century BC, as they had been moving southwards aggressively, at the expense of Gallic tribes, and establishing a Germanic presence in the immediate areas north of the Danube. In particular, he saw the Suebians as the most warlike of the Germanic peoples.
During the reign of Augustus the first emperor, Rome made aggressive campaigns into Germania, east of the Rhine and north of the Danube, pushing towards the Elbe. After suffering a major defeat to the Romans in 9 BC, Maroboduus became king of a Suevian kingdom which was established within the protective mountains and forests of Bohemia. The Suevians did not join the alliance led by Arminius.
By the Crisis of the Third Century, new Suebian groups had emerged, and Italy was invaded again by the Juthungi, while the Alamanni ravaged Gaul and settled the Agri Decumates. The Alamanni continued exerting pressure on Gaul, while the Alamannic chieftain Chrocus played an important role in elevating Constantine the Great to Roman Emperor.
By the late 4th century AD, the Middle Danubian frontier inhabited by the Quadi and Marcomanni received large numbers of Gothic and other eastern peoples escaping disturbances associated with the Huns. In 406 AD, Suebian tribes led by Hermeric, together with other Danubian groups including Alans and Vandals, crossed the Rhine and overran Gaul and Hispania. They eventually established the Kingdom of the Suebi in northwestern Spain and Portugal. With the breaking up of Hunnic power after the Battle of Nedao there was also a short-lived Kingdom of the Suebi on the Danube, under Hunimund. They were defeated by the Ostrogoths, one of the peoples of eastern origin who had been allies of the Huns. In the sixth century the Suevic Longobards moved from the Elbe to become one of the major powers of the Middle Danube, in competition with the dynasties from the east such as the Herules, Gepids and Ostrogoths.
During the last years of the decline of the Western Roman Empire, the Suebian general Ricimer was its de facto ruler. The Lombards, with many Danubian peoples both Suebian and eastern, later settled Italy and established the Kingdom of the Lombards.
The Alamanni, Bavarii and Thuringii who remained in Germania gave their names to the still-existing German regions of Swabia, Bavaria and Thuringia respectively. Suebian languages are thought to be the main source of the later High German languages, including standard German and the dialects predominant in Southern Germany, Switzerland and Austria, which experienced the Second consonant shift some time after about 600 AD. And given the closeness to these dialects to Dutch and Low German, it is likely that Suebian languages also strongly influenced the development of those languages as well.