The Suebi (or Suevi, Suavi, or Suevians) were a large group of tribes who lived in Germania in the time of the Roman Empire. They were first mentioned by Julius Caesar in connection with his battles against Ariovistus in Gaul, around 58 BC. While Caesar treated them as one Germanic tribe within an alliance, but the largest and most warlike one, later authors, such as Tacitus, Pliny the Elder and Strabo, specified that the Suevi "do not, like the Chatti or Tencteri, constitute a single nation. They actually occupy more than half of Germania, and are divided into a number of distinct tribes under distinct names, though all generally are called Suebi". At one time, classical ethnography had applied the name Suevi to so many Germanic tribes that it appeared as if, in the first centuries AD, that native name would replace the foreign name "Germans".
Classical authors noted that the Suevic tribes, compared to other Germanic tribes, were very mobile and not reliant on agriculture. Various Suevic groups moved from the direction of the Baltic Sea and the Elbe, becoming a periodic threat to the Roman Empire on their Rhine and Danube frontiers. Towards the end of the empire, the Alemanni, also referred to as Suebi, first settled in the Agri Decumates and then crossed the Rhine and occupied Alsace. An area in southwest Germany is still called Swabia, which name derives from the Suebi. (In a broader sense, their eastern neighbours, the Bavarians and Thuringii, can be said to have Suebic ancestry.) Other Suebi entered Gaul and some moved as far as Gallaecia (modern Galicia, in Spain, and Northern Portugal), where they established the Kingdom of the Suebi, which lasted for 170 years until its integration into the Visigothic Kingdom. More generally, the Suebian language and culture is associated with the Irminones and thought to encompass the "High German" cultures and dialects of the Thuringii, Bavarians and Lombards, among others.