The Marcomanni were a Germanic tribal confederation who eventually came to live in a powerful kingdom north of the Danube, coming to live in a kingdom somewhere in the region near modern Bohemia, during the peak of power of the nearby Roman empire. According to Tacitus and Strabo they were Suebian.
It is believed their name derives possibly from the Proto-Germanic forms of "march" ("frontier, border") and "men", *Markōmanniz, which would have been rendered in Latin form as Marcomanni.
The Marcomanni first appear in historical records as confederates of the Suebi of Ariovistus fighting against Julius Caesar in Gaul (modern France), having crossed the Rhine from southern Germany. The exact position of their lands at this time is not known. The fact that their name existed before the Romans had territory near the Danube or Rhine raises the question of which border they lived near in order to explain their name. It has been suggested that they may have lived near the conjunction of Rhine and Main river. However the historian Florus reports that Drusus erected a mound of their spoils during his campaign of 12-9 BC, after defeating the Tencteri and Chatti, and before next turning to Cherusci, Suevi, and Sicambri, suggesting that they were not close to any obvious border at the time.
According to the accounts of Tacitus (Germ. 42), Paterculus (2.108), Pliny the elder, and Strabo (vii. p. 290) they eventually moved into the large area previously occupied by the Boii, specifically in a region already called Baiohaemum, where their allies and fellow Suevi the Quadi lived. This was described as being within the Hercynian forest and was possibly in the region of modern Bohemia, although this is not certain. By 6 BC their king Maroboduus had established a powerful kingdom there that Augustus perceived as a threat to Rome. Before he could act, however, the revolt in Illyria intervened. Eventually Maroboduus was deposed and exiled by Catualda (AD 19). Catualda was in turn deposed by Vibilius of the Hermunduri the same year, and succeeded by the Quadian Vannius. Around 50 AD, Vannius was himself also deposed by Vibilius, in coordination with his nephews Vangio and Sido.