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, beyond the fact that it must be west of Bohemia, where they moved to later according to the accounts of Tacitus (Germ. 42), Paterculus (2.108), and Strabo (vii. p. 290). This 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.
To escape Roman aggression by 6 BC they had migrated east to Bohemia, land previously inhabited by the Celtic Boii, where their king Maroboduus established a powerful kingdom 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.
Tacitus, in the late 1st century mentions (Germania I.42) the Marcomanni as being under kings appointed by Rome. 
In the 2nd century AD, the Marcomanni entered into a confederation with other peoples including the Quadi, Vandals, and Sarmatians, against the Roman Empire. This was probably driven by movements of larger tribes, like the Goths. According to the historian Eutropius, the forces of the Emperor Marcus Aurelius battled against the Marcomannic confederation for three years at the fortress of Carnuntum in Pannonia. Eutropius compared the war, and Marcus Aurelius' success against the Marcomanni and their allies, to the Punic Wars. The comparison was apt in that this war marked a turning point and had significant Roman defeats; it caused the death of two Praetorian Guard commanders. The war began in 166, when the Marcomanni overwhelmed the defences between Vindobona and Carnuntum, penetrated along the border between the provinces of Pannonia and Noricum, laid waste to Flavia Solva, and could be stopped only shortly before reaching Aquileia on the Adriatic sea. The war lasted until Marcus Aurelius' death in 180. It would prove to be only a limited success for Rome; the Danube river remained as the frontier of the Empire until the final fall of the West.
There is a runic alphabet called the Marcomannic runes, but they are not believed to be related to the Marcomannic people.
After crossing the Pyrenees in 409, a group of Marcomanni, Quadi and Buri, established themselves in the Roman province of Gallaecia (modern Galicia and northern Portugal), where they were considered foederati and founded the Suebi Kingdom of Gallaecia. There, Hermeric swore fealty to the Emperor in 410. Bracara Augusta, the modern city of Braga in Portugal, previously the capital of Roman Gallaecia, now became the capital of the Suebic kingdom.
Kings of the Marcomanni
- List of ancient Germanic peoples
- Migrations period
- Timeline of Germanic kingdoms
- History of Portugal
- Galicia (Spain)
- History of Spain
- Caesar De Bello Gallico, at The Latin Library
- Tacitus Germania, at The Latin Library
- Tacitus Annales, at The Latin Library